Edgar Filing: AMERICAN TOWER CORP /MA/

FORM S-4

As filed with the Securities and Exchange Commission on May 27, 2005

Registration No. 333-[·]

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-4

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

AMERICAN TOWER CORPORATION

(Exact Name of Registrant as Specified in Its Charter)

Delaware

4899

65-0723837

(State or Other Jurisdiction of Incorporation or Organization)

(Primary Standard Industrial Classification Code Number)

(I.R.S. Employer

Identification No.)

116 Huntington Avenue

Boston, Massachusetts 02116

(617) 375-7500

(Address, Including Zip Code, and Telephone Number,

Including Area Code, of Registrant’s Principal Executive Offices)

James D. Taiclet, Jr.

Chairman, President and Chief Executive Officer

American Tower Corporation

116 Huntington Avenue

Boston, Massachusetts 02116

(617) 375-7500

(Name, Address, Including Zip Code, and Telephone Number,

Including Area Code, of Agent for Service)

Copies to:

Matthew J. Gardella, Esq.

Palmer & Dodge LLP

111 Huntington Avenue

Boston, Massachusetts 02199-7613

Tel: (617) 239-0100

Fax: (617) 227-4420

John L. Graham, Esq.

King & Spalding LLP

1185 Avenue of the Americas

New York, NY 10036-4003

Tel: (212) 556-2100

Fax: (212) 556-2222

Bruce A. Gutenplan, Esq.

Raphael M. Russo, Esq.

Paul, Weiss, Rifkind, Wharton

& Garrison LLP

1285 Avenue of the Americas

New York, New York 10019-6064

Tel: (212) 373-3000

Fax: (212) 757-3990

Approximate date of commencement of proposed sale of the securities to the public: As soon as practicable following consummation of the merger described in this registration statement.

If the securities being registered on this form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box. ¨

If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ¨

If this form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ¨

CALCULATION OF REGISTRATION FEE


Title of each class of securities to be registered	Amount to be registered(1)		Proposed maximum offering price per unit	Proposed maximum aggregate offering price			Amount of registration fee
Class A common stock, $0.01 par value	186,468,275	(2)	N/A	$	3,177,784,516	(3)	$	374,026	(3)

(1)

This Registration Statement relates to Class A common stock, par value $0.01 per share, of American Tower Corporation (“American Tower”) issuable to holders of common stock, par value $0.01 per share, of SpectraSite, Inc. (“SpectraSite”) in the proposed merger of SpectraSite with Asteroid Merger Sub, LLC, a wholly owned subsidiary of American Tower.

(2)	This Registration Statement shall cover any additional shares of American Tower Class A common stock that become issuable to SpectraSite stockholders by reason of an adjustment in the exchange ratio as a result of any stock dividend, stock split, recapitalization or other similar transaction.

(3)	The registration fee was calculated pursuant to Rule 457(f)(1) as $60.925 (the average of the high and low prices of SpectraSite common stock on the New York Stock Exchange on May 20, 2005), multiplied by 52,158,958 fully diluted shares.

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

The information contained in this joint proxy statement/prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This joint proxy statement/prospectus is not an offer to sell these securities and is not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

Subject to completion, dated May 27, 2005

JOINT PROXY STATEMENT/PROSPECTUS

To the stockholders of American Tower Corporation and SpectraSite, Inc.

The boards of directors of American Tower Corporation and SpectraSite, Inc. have agreed to a merger pursuant to which SpectraSite will merge with a subsidiary of American Tower. If the merger is consummated, holders of SpectraSite common stock will receive 3.575 shares of American Tower Class A common stock for each share of SpectraSite common stock that they own. As a result, and based upon the outstanding American Tower Class A common stock and SpectraSite common stock as of May 20, 2005, SpectraSite stockholders will hold approximately 42% of the American Tower Class A common stock outstanding immediately after the merger.

SpectraSite common stock trades on the New York Stock Exchange under the symbol “SSI.” On May 20, 2005, the closing price of SpectraSite common stock was $61.08 per share. American Tower Class A common stock trades on the New York Stock Exchange under the symbol “AMT.” On May 20, 2005, the closing price of American Tower Class A common stock was $17.20 per share. As of May 20, 2005, American Tower would be obligated to issue up to approximately 186.5 million shares of Class A common stock in the merger, including shares issuable pursuant to outstanding SpectraSite stock options and warrants.

The boards of directors of both American Tower and SpectraSite have unanimously approved the merger. The SpectraSite board of directors unanimously recommends that the SpectraSite stockholders vote “FOR” the approval of the SpectraSite merger proposal. The American Tower board of directors unanimously recommends that the American Tower stockholders vote “FOR” the approval of the American Tower merger proposal.

This joint proxy statement/prospectus provides the stockholders of American Tower and SpectraSite with detailed information about the merger agreement and the merger. We encourage you to read this joint proxy statement/prospectus carefully in its entirety, including all of its annexes. In particular, you should carefully read the section captioned “ RISK FACTORS” beginning on page 16 for a discussion of certain risk factors relating to the merger, American Tower and SpectraSite, as well as the risk factors found in the American Tower and SpectraSite documents that are incorporated by reference. You may obtain additional information about American Tower and SpectraSite from documents American Tower and SpectraSite, respectively, have filed with the Securities and Exchange Commission by following the procedures discussed under the section captioned “WHERE YOU CAN FIND MORE INFORMATION” beginning on page 114 of this joint proxy statement/prospectus.

Consummation of the merger requires the approval of both the SpectraSite stockholders and the American Tower stockholders. Your vote is very important. American Tower and SpectraSite stockholders will be asked to vote on proposals for the merger at their respective special stockholders meetings. The dates, times and places of the special meetings are as follows:

American Tower Special Stockholders Meeting

[·], 2005

[·] a.m., local time

Palmer & Dodge LLP

111 Huntington Avenue

Boston, Massachusetts

SpectraSite Special Stockholders Meeting

[·], 2005

[·] a.m., local time

SpectraSite, Inc.

400 Regency Forest Drive

Cary, North Carolina

Whether or not you expect to attend your special meeting, please complete, date, sign and return the accompanying proxy in the enclosed postage paid envelope so that your shares may be represented at your special meeting. Returning the proxy does not deprive you of your right to attend the meeting and vote your shares in person. In addition, stockholders may also vote over the Internet or by telephone by following the instructions on the accompanying proxy card.

LOGO

James D. Taiclet, Jr.

Chairman of the Board, President

and Chief Executive Officer of American Tower

LOGO

Stephen H. Clark

Chairman of the Board, President

and Chief Executive Officer of SpectraSite

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to be issued in connection with the merger or determined if this joint proxy statement/prospectus is accurate or complete. Any representation to the contrary is a criminal offense.

This joint proxy statement/prospectus is dated [·], 2005 and is first being mailed to SpectraSite stockholders and American Tower stockholders on or about [·], 2005.

ADDITIONAL INFORMATION

This joint proxy statement/prospectus incorporates important business and financial information about American Tower and SpectraSite from other documents that are not included in or delivered with this joint proxy statement/prospectus. This information is available to you without charge upon your written or oral request. You can obtain the documents incorporated by reference in this joint proxy statement/prospectus by accessing the Internet website maintained by the Securities and Exchange Commission, which we refer to as the SEC, at http://www.sec.gov or by requesting them in writing or by telephone from the appropriate company at one of the following addresses:

American Tower Corporation

Investor Relations

116 Huntington Avenue

Boston, Massachusetts 02116

Tel: (617) 375-7500

SpectraSite, Inc.

Investor Relations

400 Regency Forest Drive

Cary, North Carolina 27511

Tel: (919) 466-5492

To obtain timely delivery, you must request any documents no later that five business days before the special meetings. Accordingly, please request any documents by [·], 2005 to receive them before the special meetings.

See the section captioned “WHERE YOU CAN FIND MORE INFORMATION” beginning on page 114.

ABOUT THIS DOCUMENT

This document, which forms part of a registration statement on Form S-4 filed with the SEC by American Tower, constitutes a prospectus of American Tower under Section 5 of the Securities Act of 1933, as amended, which we refer to as the Securities Act, with respect to the shares of American Tower Class A common stock to be issued to the holders of SpectraSite common stock in connection with the merger. This document also constitutes a proxy statement under Section 14(a) of the Securities Exchange Act of 1934, as amended, which we refer to as the Exchange Act, and the rules thereunder, and a notice of meeting with respect to American Tower’s special meeting of stockholders and SpectraSite’s special meeting of stockholders, at which, among other things, the stockholders of each company will consider and vote upon the American Tower merger proposal and the SpectraSite merger proposal, as the case may be.

LOGO

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

AMERICAN TOWER CORPORATION

[·], 2005

NOTICE IS HEREBY GIVEN that the Special Meeting of Stockholders of American Tower Corporation, a Delaware corporation, will be held at Palmer & Dodge LLP, 111 Huntington Avenue, Boston, Massachusetts, on [·], 2005, beginning at [·] a.m., local time for the purpose of considering and voting on the following matters:

To approve the issuance of shares of American Tower Class A common stock pursuant to the Agreement and Plan of Merger, dated as of May 3, 2005, by and among American Tower Corporation, Asteroid Merger Sub, LLC and SpectraSite, Inc., a copy of which is attached as Annex A to this joint proxy statement/prospectus;

To approve a proposal to amend and restate American Tower’s Restated Certificate of Incorporation if the merger is consummated, as more fully described in this joint proxy statement/prospectus, which approval is not a condition to the merger;

To permit American Tower’s board of directors or its chairman, in their discretion, to adjourn or postpone the special meeting if necessary for further solicitation of proxies if there are not sufficient votes at the originally scheduled time of the special meeting to approve any of the foregoing proposals; and

To act upon such other matters as may properly come before the meeting or any adjournments or postponements thereof.

The business to be conducted at the meeting is more fully described in this joint proxy statement/prospectus. As of the date of this notice, American Tower’s board of directors knows of no other business to be conducted at the special meeting.

American Tower’s board of directors has fixed the close of business on [·], 2005 as the record date for the determination of American Tower stockholders entitled to notice of, and to vote at, the special meeting and at any continuation or adjournment of the meeting. During the ten-day period before the special meeting, American Tower will keep a list of stockholders entitled to vote at the special meeting available for inspection during normal business hours at its offices in Boston, Massachusetts, for any purpose germane to the special meeting. The list of stockholders will also be provided and kept at the location of the special meeting for the duration of the special meeting, and may be inspected by any stockholder who is present. All persons wishing to be admitted to the special meeting must present photo identification. Please also note that if you hold your shares in “street name” through a broker or other nominee, you will need to bring a copy of a brokerage statement reflecting your stock ownership as of the record date and check in at the registration desk at the special meeting.

By Order of the Board of Directors

LOGO

William H. Hess

Executive Vice President,

General Counsel and Secretary

Boston, Massachusetts

[·], 2005

All American Tower stockholders are cordially invited to attend the special meeting. Whether or not you expect to attend the special meeting, please complete, date, sign and return the enclosed proxy card as promptly as possible to ensure your representation at the special meeting. A postage prepaid envelope is enclosed for that purpose. You may also vote over the Internet or by telephone by following the instructions on the enclosed proxy card. Even if you have given your proxy or voted over the Internet or by telephone, you may still vote in person if you attend the special meeting.

LOGO

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

SPECTRASITE, INC.

[·], 2005

NOTICE IS HEREBY GIVEN that the Special Meeting of Stockholders of SpectraSite, Inc., a Delaware corporation, will be held at SpectraSite, Inc., 400 Regency Forest Drive, Cary, North Carolina, on [·], 2005, beginning at [·] a.m., local time for the purpose of considering and voting on the following matters:

To approve and adopt the Agreement and Plan of Merger, dated as of May 3, 2005, by and among American Tower Corporation, Asteroid Merger Sub, LLC and SpectraSite, Inc., including the merger and the other transactions contemplated thereby, a copy of which is attached as Annex A to this joint proxy statement/prospectus;

To permit SpectraSite’s board of directors or its chairman, in their discretion, to adjourn or postpone the special meeting if necessary for further solicitation of proxies if there are not sufficient votes at the originally scheduled time of the special meeting to approve the SpectraSite merger proposal; and

To act upon such other matters as may properly come before the meeting or any adjournments or postponements thereof.

The business to be conducted at the meeting is more fully described in this joint proxy statement/prospectus. As of the date of this notice, SpectraSite’s board of directors knows of no other business to be conducted at the special meeting.

SpectraSite’s board of directors has fixed the close of business on [·], 2005 as the record date for the determination of SpectraSite stockholders entitled to notice of, and to vote at, the special meeting and at any continuation or adjournment of the meeting. During the ten-day period before the special meeting, SpectraSite will keep a list of stockholders entitled to vote at the special meeting available for inspection during normal business hours at its offices in Cary, North Carolina, for any purpose germane to the special meeting. The list of stockholders will also be provided and kept at the location of the special meeting for the duration of the special meeting, and may be inspected by any stockholder who is present. All persons wishing to be admitted to the special meeting must present photo identification. Please also note that if you hold your shares in “street name” through a broker or other nominee, you will need to bring a copy of a brokerage statement reflecting your stock ownership as of the record date and check in at the registration desk at the special meeting.

By Order of the Board of Directors

LOGO

John H. Lynch

Senior Vice President,

General Counsel and Secretary

Cary, North Carolina

[·], 2005

All SpectraSite stockholders are cordially invited to attend the special meeting. Whether or not you expect to attend the special meeting, please complete, date, sign and return the enclosed proxy card as promptly as possible to ensure your representation at the special meeting. A postage prepaid envelope is enclosed for that purpose. You may also vote over the Internet or by telephone by following the instructions on the enclosed proxy card. Even if you have given your proxy or voted over the Internet or by telephone, you may still vote in person if you attend the special meeting.

TABLE OF CONTENTS


		Page
QUESTIONS AND ANSWERS ABOUT THE MERGER		iii
SUMMARY OF THIS JOINT PROXY STATEMENT/PROSPECTUS		1
The Companies		1
The Merger		2
Reasons for the Merger		2
Recommendations of the Boards of Directors		2
Opinions of Financial Advisors		2
The Special Meetings		3
Record Dates		3
Votes Required		3
Conflicts of Interests of SpectraSite’s Directors and Executive Officers in the Merger		4
Board of Directors of American Tower after the Merger		4
Treatment of SpectraSite Stock Options, Warrants and Restricted Stock		4
Regulatory Matters		5
Material U.S. Federal Income Tax Considerations of the Merger		5
Consummation and Effectiveness of the Merger		6
Conditions to the Merger Agreement		6
“No Solicitation” Provision		6
Termination of the Merger Agreement		7
Termination Fees and Expenses		7
Accounting Treatment		7
Appraisal Rights		7
SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA		8
American Tower Selected Historical Consolidated Financial Data		8
SpectraSite Selected Historical Consolidated Financial Data		11
SELECTED UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL DATA		13
UNAUDITED COMPARATIVE PER SHARE DATA		14
COMPARATIVE PER SHARE MARKET PRICE DATA AND DIVIDEND INFORMATION		15
RISK FACTORS		16
Risks Associated with the Merger		16
Risks Associated with American Tower Following the Merger		19
Risks Associated with American Tower’s Business		23
Risks Associated with SpectraSite’s Business		23
THE AMERICAN TOWER SPECIAL MEETING		24
Joint Proxy Statement/Prospectus		24
Date, Time and Place of the Special Meeting		24
Purpose of the Special Meeting		24


		Page
Stockholder Record Date for the Special Meeting		24
Quorum; Vote Required for Each Proposal		25
Adjournment or Postponement		26
Proxies		26
Solicitation of Proxies		27
THE SPECTRASITE SPECIAL MEETING		28
Joint Proxy Statement/Prospectus		28
Date, Time and Place of the Special Meeting		28
Purpose of the Special Meeting		28
Stockholder Record Date for the Special Meeting		28
Quorum; Vote Required for Each Proposal		28
Adjournment or Postponement		29
Proxies		29
Appraisal Rights		30
Solicitation of Proxies		30
PROPOSAL NUMBER ONE: THE MERGER PROPOSALS		31
General Description of the Merger		31
Background of the Merger		31
American Tower’s Reasons for the Merger		40
Recommendation of American Tower’s Board of Directors		42
Opinion of American Tower’s Financial Advisor		42
SpectraSite’s Reasons for the Merger		50
Recommendation of SpectraSite’s Board of Directors		53
Opinions of SpectraSite’s Financial Advisors		53
Lehman Brothers’ and Evercore’s Analysis		57
Conflicts of Interests of SpectraSite Directors and Executive Officers in the Merger		63
Consummation and Effectiveness of the Merger		65
Conversion of SpectraSite Common Stock		65
Treatment of SpectraSite Stock Options		65
Treatment of SpectraSite’s Warrants		66
Treatment of SpectraSite’s Restricted Stock		66
Board of Directors, Officers and Governing Documents of American Tower after the Merger		67
Regulatory Matters		67
Accounting Treatment of the Merger		68
Restrictions on Sales of Shares by Affiliates of SpectraSite		68
Appraisal Rights		68
Delisting and Deregistration of SpectraSite Common Stock after the Merger		68
MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS OF THE MERGER		69
General		70
Certain Additional Tax Considerations of the Merger to Non-U.S. Holders		71


		Page
Tax Opinions as Condition to Merger		71
Reporting Requirements		72
Information Reporting and Backup Withholding		72
THE MERGER AGREEMENT		73
Form of Merger		73
Consummation and Effectiveness of the Merger		73
Consideration to be Received in the Merger		73
Procedures for Exchange of Certificates		74
Conditions to Consummation of the Merger		75
Representations and Warranties		76
Conduct of Business by American Tower and SpectraSite Prior to Consummation of the Merger		78
No Solicitation		80
Termination of the Merger Agreement		83
Expenses and Termination Fees		85
Filings Under the HSR Act; Reasonable Best Efforts		87
Indemnification and Insurance		87
Board of Directors of the Combined Company		88
Consents and/or Amendments of Certain Bank Lenders		88
Consent Solicitation; Supplemental Indenture; Tender Offer		88
Employees		89
Amendment and Waiver		89
Governing Law		89
AMERICAN TOWER DESCRIPTION OF CAPITAL STOCK		90
General		90
Preferred Stock		90
Common Stock		91
Dividend Restrictions		93
Delaware Business Combination Provisions		93
Listing of Class A Common Stock		93
Transfer Agent and Registrar		93
UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION		94
COMPARISON OF RIGHTS OF AMERICAN TOWER STOCKHOLDERS AND SPECTRASITE STOCKHOLDERS		100


		Page
AMERICAN TOWER STOCKHOLDERS ONLY—AMERICAN TOWER PROPOSAL NUMBER TWO: TO AMEND AND RESTATE THE AMERICAN TOWER CORPORATION RESTATED CERTIFICATE OF INCORPORATION		103
Purpose and Effect of Amended and Restated Certificate of Incorporation		103
Vote Required		104
Recommendation of the Board of Directors		104
AMERICAN TOWER STOCKHOLDERS ONLY—AMERICAN TOWER PROPOSAL NUMBER THREE: POSSIBLE ADJOURNMENT OF THE AMERICAN TOWER SPECIAL MEETING		105
SPECTRASITE STOCKHOLDERS ONLY—SPECTRASITE PROPOSAL NUMBER TWO: POSSIBLE ADJOURNMENT OF THE SPECTRASITE SPECIAL MEETING		106
AMERICAN TOWER PRINCIPAL STOCKHOLDERS		107
SPECTRASITE PRINCIPAL STOCKHOLDERS		109
FUTURE STOCKHOLDER PROPOSALS		111
LEGAL MATTERS		112
EXPERTS		113
WHERE YOU CAN FIND MORE INFORMATION		114
STATEMENT REGARDING FORWARD-LOOKING INFORMATION		116
ANNEX A AGREEMENT AND PLAN OF MERGER		A-1
ANNEX B OPINION OF CITIGROUP GLOBAL MARKETS INC.		B-1
ANNEX C OPINION OF LEHMAN BROTHERS INC.		C-1
ANNEX D OPINION OF EVERCORE GROUP INC.		D-1
ANNEX E AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF AMERICAN TOWER CORPORATION		E-1

QUESTIONS AND ANSWERS ABOUT THE MERGER

Q:	Why are American Tower and SpectraSite proposing the merger?

The boards of directors of American Tower and SpectraSite believe that the merger will provide strategic and financial benefits to the stockholders of both companies. The boards of directors of both companies believe that the merger has the potential to result in cost savings and will enhance the position of the combined company in the wireless communications tower industry due to the increase in the size and quality of the combined company’s U.S. communications tower portfolio and the improved ability of the combined company to satisfy the needs of its wireless carrier customers.

Q:	What will I receive in the merger?

If the merger is consummated, SpectraSite stockholders will receive 3.575 shares of American Tower Class A common stock for each share of SpectraSite common stock that they own. SpectraSite stockholders will also receive a cash payment for any fractional shares. For example, a SpectraSite stockholder owning 100 shares of SpectraSite common stock will receive 357 shares of American Tower Class A common stock and a cash payment equal to the value of one half share of American Tower Class A common stock.

If the merger is consummated, SpectraSite common stock will no longer be traded publicly, and the combined company will continue to be traded on the New York Stock Exchange, which we refer to as the NYSE, under the symbol “AMT”.

If the merger is consummated, American Tower stockholders will continue to hold their existing American Tower Class A common stock. Based upon the outstanding American Tower Class A common stock and SpectraSite common stock as of May 20, 2005, American Tower stockholders will hold approximately 58% of the American Tower Class A common stock outstanding immediately after the merger.

Q:	Who is entitled to vote at my company’s special meeting?

A:	American Tower. Holders of record of American Tower Class A common stock as of the close of business on [·], 2005 will be entitled to notice of and to vote at the American Tower special meeting.

SpectraSite. Holders of record of SpectraSite common stock as of the close of business on [·], 2005 will be entitled to notice of and to vote at the SpectraSite special meeting.

Q:	What stockholder approvals are needed?

The transactions contemplated by the merger agreement will not be consummated unless the merger proposal is approved (1) by holders of a majority of the shares of American Tower Class A common stock voting on such proposal, provided that the total votes cast represents over 50% in interest of all securities entitled to vote, and (2) by holders of a majority of the outstanding shares of SpectraSite common stock.

Approval of the proposal to amend and restate American Tower’s certificate of incorporation requires the approval of holders of at least 66²/3% of the outstanding shares of American Tower Class A common stock. As further discussed below, the American Tower merger proposal is not conditioned on the approval of the proposal to amend and restate American Tower’s certificate of incorporation; however, the proposal to amend and restate American Tower’s certificate of incorporation is conditioned on the consummation of the merger.

Approval of the proposal to permit American Tower’s board of directors or its chairman to adjourn or postpone the American Tower special meeting to a later date for the purpose of soliciting additional proxies requires the approval of holders of a majority of the shares of American Tower Class A common stock voting on such proposal.

iii

Approval of the proposal to permit SpectraSite’s board of directors or its chairman to adjourn or postpone the SpectraSite special meeting to a later date for the purpose of soliciting additional proxies requires the approval of holders of a majority of the shares of SpectraSite common stock voting on such proposal.

Each holder of American Tower Class A common stock is entitled to one vote per share, and each holder of SpectraSite common stock is entitled to one vote per share.

Q:	How do I vote?

A:	If you are a stockholder of record of American Tower as of the record date for the American Tower special meeting or a stockholder of record of SpectraSite as of the record date for the SpectraSite special meeting, you may vote in person by attending your stockholders’ meeting, or you may vote by:

•

Internet: by accessing the Internet website specified on your proxy card;

•

Telephone: by calling the toll-free number specified on your proxy card; or

•

Mail: by signing, dating and mailing the enclosed proxy card so that your shares may be represented and voted at your stockholders’ meeting.

Q:	When and where will my company’s special meeting be held?

A:	American Tower. The American Tower special meeting will be held on [·], 2005 at [·] a.m., local time, at Palmer & Dodge LLP, 111 Huntington Avenue, Boston, Massachusetts.

SpectraSite. The SpectraSite special meeting will be held on [·], 2005 at [·] a.m., local time, at SpectraSite, Inc., 400 Regency Forest Drive, Cary, North Carolina.

Q:	Does my company’s board of directors recommend the approval of the merger proposal?

Yes. The American Tower board of directors has unanimously approved and adopted the merger agreement, the merger and the other transactions contemplated by the merger agreement. The American Tower board of directors has determined that the merger is consistent with and in furtherance of the long-term business strategy of American Tower and in the best interests of American Tower and the holders of American Tower Class A common stock, and therefore unanimously recommends that American Tower stockholders vote “FOR” the approval of the American Tower merger proposal. The factors considered by the American Tower board of directors are described in the section captioned “PROPOSAL NUMBER ONE: THE MERGER PROPOSALS—American Tower’s Reasons for the Merger” beginning on page 40.

The SpectraSite board of directors has unanimously approved and adopted the merger agreement, the proposed merger and the other transactions contemplated by the merger agreement. The SpectraSite board of directors has determined that the merger is consistent with and in furtherance of the long-term business strategy of SpectraSite and in the best interests of SpectraSite and the holders of SpectraSite common stock, and therefore unanimously recommends that SpectraSite stockholders vote “FOR” the approval of the SpectraSite merger proposal. The factors considered by the SpectraSite board of directors are described in the section captioned “PROPOSAL NUMBER ONE: THE MERGER PROPOSALS—SpectraSite’s Reasons for the Merger” beginning on page 50.

Q:	What changes are being proposed to American Tower’s certificate of incorporation?

A:	The American Tower stockholders are being asked to approve a proposal to amend and restate American Tower’s Restated Certificate of Incorporation to:

•

Increase the authorized number of shares of Class A common stock from 500.0 million shares to 1.0 billion shares;

•

Eliminate references to the authorized shares of Class B common stock and

Class C common stock, of which none are currently outstanding;

•

Lower the threshold to amend certain provisions of American Tower’s certificate of incorporation from 66²/3% of the outstanding shares of American Tower common stock to a majority of the outstanding shares of American Tower common stock;

•

Eliminate voting power limitations that were applicable to certain holders of Class B common stock; and

•

Make other conforming changes in connection with the foregoing.

The full text of the proposed Amended and Restated Certificate of Incorporation is attached as Annex E to this joint proxy statement/prospectus. The American Tower board of directors unanimously recommends that American Tower stockholders vote “FOR” the approval of the proposal to amend and restate American Tower’s certificate of incorporation.

Q:	Is the American Tower merger proposal conditioned on the approval of the proposal to amend and restate the certificate of incorporation of American Tower?

No. The American Tower merger proposal is not conditioned on the proposal to amend and restate American Tower’s certificate of incorporation. Although American Tower currently has sufficient authorized shares of Class A common stock to consummate the merger, American Tower is seeking to amend and restate its certificate of incorporation to, among other things, increase the number of authorized shares. In connection with the merger, American Tower is obligated to issue up to approximately 186.5 million shares of Class A common stock, including approximately 168.2 million shares issuable at the closing with respect to outstanding shares of SpectraSite common stock as of May 20, 2005 and up to approximately 18.3 million shares issuable pursuant to outstanding SpectraSite stock options and warrants as of May 20, 2005. As a result, after consummation of the merger, American Tower would only have approximately 9.3 million authorized shares of Class A common stock that are not already issued or reserved for issuance pursuant to outstanding options, warrants, convertible notes and its employee stock purchase plan as of May 20, 2005. The American Tower board of directors believes that it is advisable and in the best interests of the stockholders to have available additional authorized but unissued shares in an amount adequate to provide for future needs.

Q:	Is the proposal to amend and restate the certificate of incorporation of American Tower conditioned on the consummation of the merger?

Yes. The proposal to amend and restate American Tower’s certificate of incorporation is conditioned on the consummation of the merger. Accordingly, if the American Tower merger proposal is not approved or the merger is not consummated for any other reason, American Tower will not amend and restate its certificate of incorporation as set forth in this joint proxy statement/prospectus, even if approved by the American Tower stockholders.

Q:	What do I need to do now?

After carefully reading and considering the information contained in this joint proxy statement/prospectus, please respond by either (1) voting over the Internet by following the instructions on your proxy card, (2) voting by telephone by following the instructions on your proxy card or (3) completing, signing and dating your proxy card and returning it in the enclosed postage paid envelope.

If your shares are held in “street name” by your broker, you should follow the directions provided by your broker. Your broker will vote your shares only if you provide instructions on how you would like your shares to be voted.

Q:	What if I don’t vote or I abstain?

• If you are an American Tower stockholder and either fail to respond or respond and abstain from voting, it will have no effect on the vote to approve the American Tower merger proposal; however, it will have the same effect as a vote against the proposal to amend and restate American Tower’s certificate of incorporation.

•

If you are a SpectraSite stockholder and either fail to respond or respond and abstain from voting, it will have the same effect as a vote against the SpectraSite merger proposal.

•

If you are a stockholder of either American Tower or SpectraSite and respond but do not indicate how you want to vote, your proxy will be counted as a vote in favor of the American Tower or SpectraSite merger proposal, as the case may be, and will be counted as a vote in favor of the proposal to amend and restate American Tower’s certificate of incorporation in the event you are an American Tower stockholder.

Q:	Can I change my vote after I have delivered my proxy?

Yes. You can change your vote at any time before your proxy is voted at your special meeting. To revoke your proxy, you must either (1) notify the secretary of American Tower or SpectraSite, as applicable, in writing, (2) mail a new proxy card dated after the date of the proxy you wish to revoke, (3) submit a later dated proxy over the Internet or by telephone by following the instructions on your proxy card or (4) attend the special meeting and vote your shares in person. Merely attending the special meeting will not constitute revocation of your proxy. If your shares are held in an account at a brokerage firm or bank, you should contact your brokerage firm or bank to change your vote.

Q:	Should I send in my SpectraSite stock certificates now?

A:	No. After the merger is consummated, SpectraSite stockholders will receive written instructions from the exchange agent on how to exchange SpectraSite stock certificates for shares of American Tower. Please do not send in your SpectraSite stock certificates with your proxy.

Q:	When do you expect the merger to be consummated?

The merger will be consummated and become effective after all of the conditions to closing of the merger set forth in the merger agreement are satisfied or waived in accordance with the merger agreement. American Tower and SpectraSite are working to consummate the merger as quickly as possible and hope to consummate the merger before the end of the second half of 2005.

Q:	Who can help answer my questions?

A:	If you have any questions about the merger or how to submit your proxy, or if you need additional copies of this joint proxy statement/prospectus or the enclosed proxy card, you should contact:

•

if you are an American Tower stockholder:

Investor Relations

American Tower Corporation

116 Huntington Avenue

Boston, Massachusetts 02116

Tel: (617) 375-7500

•

if you are a SpectraSite stockholder:

Investor Relations

SpectraSite, Inc.

400 Regency Forest Drive, Suite 400

Cary, North Carolina 27511

Tel: (919) 466-5492

SUMMARY OF THIS JOINT PROXY STATEMENT/PROSPECTUS

This summary highlights selected information in this joint proxy statement/prospectus. While American Tower and SpectraSite believe this summary highlights the material information contained in this joint proxy statement/prospectus, this summary may not contain all of the information that is important to you. You should carefully read this entire joint proxy statement/prospectus and the other documents to which we refer for a more complete understanding of the merger. This summary and the balance of this joint proxy statement/prospectus contain forward-looking statements about events that are not certain to occur, and you should not place undue reliance on those statements. Please carefully read the sections captioned “WHERE YOU CAN FIND MORE INFORMATION” and “STATEMENT REGARDING FORWARD-LOOKING INFORMATION” beginning on pages 114 and 116, respectively.

The Companies

American Tower Corporation

116 Huntington Avenue

Boston, Massachusetts 02116

Tel: (617) 375-7500

Fax: (617) 375-7575

www.americantower.com

American Tower is a leading wireless and broadcast communications infrastructure company with a portfolio of over 14,800 towers. Its primary business is leasing antenna space on multi-tenant communications towers to wireless service providers and radio and television broadcast companies. It owns and operates towers throughout the United States and Mexico, as well as in selected markets in Brazil. It operates the largest independent portfolio of wireless communications and broadcast towers in the United States and Mexico, based on number of towers and revenue.

American Tower operates in two business segments: rental and management and network development services. American Tower’s primary business is its leasing business, which American Tower refers to as its rental and management segment. American Tower also offers tower related services through its network development services segment that are complementary to its rental and management segment. In November 2004, American Tower sold its tower construction services unit, which constituted a significant component of its network development services segment. Since that sale, American Tower’s remaining network development services segment has continued to provide non-construction services, including site acquisition, zoning, permitting and structural analysis.

You should not consider the information on American Tower’s website to be part of this joint proxy statement/prospectus.

SpectraSite, Inc.

400 Regency Forest Drive

Cary, North Carolina 27511

Tel: (888) 468-0112

Fax: (919) 468-8522

www.spectrasite.com

SpectraSite is one of the largest wireless tower operators in the United States. At December 31, 2004, SpectraSite owned or operated approximately 10,000 revenue producing sites, including 7,821 towers and in-building systems primarily in the top 100 markets in the United States. SpectraSite’s customers are leading wireless communications providers, including Cingular Wireless, Nextel, Sprint PCS, T-Mobile and Verizon Wireless.

You should not consider the information on SpectraSite’s website to be part of this joint proxy statement/prospectus.

Asteroid Merger Sub, LLC

116 Huntington Avenue

Boston, Massachusetts 02116

Tel: (617) 375-7500

Fax: (617) 375-7575

Asteroid Merger Sub, LLC is a Delaware limited liability company and a wholly owned subsidiary of American Tower recently formed for the sole purpose of effecting the merger as described in this joint proxy statement/prospectus.

The Merger (see page 73)

A copy of the Agreement and Plan of Merger, dated as of May 3, 2005, which we refer to as the merger agreement, is attached as Annex A to this joint proxy statement/prospectus. American Tower and SpectraSite encourage you to read the entire merger agreement carefully.

Under the merger agreement, SpectraSite will merge with and into Asteroid Merger Sub. The merger will result in each share of SpectraSite common stock being converted into the right to receive 3.575 shares of American Tower Class A common stock. Following the merger, the merger agreement provides that Asteroid Merger Sub will be the surviving entity. However, American Tower may elect to have SpectraSite be the surviving entity subject to the satisfaction or waiver of certain agreements and conditions, including the receipt by each of American Tower and SpectraSite from its respective legal counsel on the closing date of the merger of opinions stating that the merger so structured will be treated for U.S. federal income tax purposes as a “reorganization” within the meaning of Section 368(a) of the Internal Revenue Code of 1986, as amended, which we refer to as the Internal Revenue Code, and that American Tower and SpectraSite will each be a party to that reorganization within the meaning of Section 368(b) of the Internal Revenue Code.

Reasons for the Merger (see pages 40 and 50)

To American Tower Stockholders: In reaching its decision to approve the merger agreement, the American Tower board of directors considered a number of factors, which are described in the section captioned “PROPOSAL NUMBER ONE: THE MERGER PROPOSALS—American Tower’s Reasons for the Merger” beginning on page 40.

To SpectraSite Stockholders: In reaching its decision to approve the merger agreement, the SpectraSite board of directors has considered a number of factors, which are described in the section captioned “PROPOSAL NUMBER ONE: THE MERGER PROPOSALS—SpectraSite’s Reasons for the Merger” beginning on page 50.

Recommendations of the Boards of Directors

(see pages 42 and 53)

To American Tower Stockholders: The American Tower board of directors believes that the merger is consistent with and in furtherance of the long-term business strategy of American Tower and in the best interests of American Tower stockholders and has unanimously voted to approve and adopt the merger agreement and unanimously recommends that American Tower stockholders vote “FOR” the approval of the American Tower merger proposal and each of the other proposals being put before the American Tower stockholders.

To SpectraSite Stockholders: The SpectraSite board of directors believes that the merger is consistent with and in furtherance of the long-term business strategy of SpectraSite and is in the best interests of SpectraSite stockholders and has unanimously voted to approve and adopt the merger agreement and unanimously recommends that SpectraSite stockholders vote “FOR” the approval of the SpectraSite merger proposal and each of the other proposals being put before the SpectraSite stockholders.

Opinions of Financial Advisors (see pages 42 and 53)

Opinion of American Tower’s Financial Advisor. In deciding to approve the merger, the American Tower board of directors considered the opinion of Citigroup Global Markets Inc., its financial advisor, that, as of the date of Citigroup’s opinion and based upon and subject to the assumptions, limitations and considerations set forth therein, the exchange ratio is fair, from a financial point of view, to American Tower. Citigroup’s opinion addresses only the fairness, from a financial point of view, of the exchange ratio to American Tower and does not address the merits of the underlying decision by American Tower to engage in the merger or constitute a recommendation to any stockholder as to how to vote with respect to the merger or any matter related thereto. The full text of the written Citigroup opinion is attached as Annex B to this joint proxy statement/prospectus. You are urged to read Citigroup’s opinion carefully in its entirety.

Opinions of SpectraSite’s Financial Advisors. Both Lehman Brothers Inc. and Evercore Group Inc. rendered oral opinions on May 3, 2005, subsequently confirmed in writing, to the SpectraSite board of directors that, as of such date, and based on and

subject to the assumptions made, matters considered and limitations on and qualifications made by each of Lehman Brothers and Evercore in its review, the exchange ratio to be offered to the holders of SpectraSite common stock in connection with the merger is fair, from a financial point of view, to the holders of SpectraSite common stock. The full text of Lehman Brothers’ and Evercore’s written opinions, each dated May 3, 2005, are attached as Annex C and Annex D, respectively, to this joint proxy statement/ prospectus. You are urged to read Lehman Brothers’ and Evercore’s opinions carefully and in their entirety. The opinions were provided for the use and benefit of the SpectraSite board of directors in connection with its consideration of the merger and were not intended to be and did not constitute a recommendation as to how any stockholders of SpectraSite or American Tower should vote with respect to the merger.

The Special Meetings (see pages 24 and 28)

American Tower. The special meeting of American Tower stockholders will be held at Palmer & Dodge LLP, 111 Huntington Avenue, Boston, Massachusetts, on [·], 2005, beginning at [·] a.m., local time.

SpectraSite. The special meeting of SpectraSite stockholders will be held at SpectraSite, Inc., 400 Regency Forest Drive, Cary, North Carolina, on [·], 2005, beginning at [·] a.m., local time.

Record Dates (see pages 24 and 28)

American Tower. If you owned shares of American Tower on [·], 2005, the record date for the American Tower special meeting, you are entitled to receive this joint proxy statement/prospectus and to vote in connection with the merger. On that date, there were [·] shares of American Tower Class A common stock outstanding, approximately [·] of which, or [·] %, were beneficially owned and entitled to vote by American Tower’s directors and executive officers. You can cast one vote for each share of American Tower Class A common stock you own.

SpectraSite. If you owned shares of SpectraSite on [·], 2005, the record date for the SpectraSite special meeting, you are entitled to receive this joint proxy statement/prospectus and to vote in connection with the merger. On that date, there were [·] shares of SpectraSite common stock outstanding, approximately [·] of which, or [·]%, were beneficially owned and entitled to vote by SpectraSite’s directors and executive officers. You can cast one vote for each share of SpectraSite common stock you own.

Votes Required (see pages 25 and 28)

American Tower. The affirmative vote of the holders of a majority of the shares of American Tower Class A common stock voting on the proposal is required to approve the American Tower merger proposal, provided that the total votes cast represents over 50% in interest of all securities entitled to vote. The affirmative vote of the holders of a majority of the shares of American Tower Class A common stock voting on the proposal is required to grant discretionary authority to American Tower’s board of directors or its chairman to adjourn or postpone the special meeting to solicit additional votes to approve the proposals presented at the special meeting.

The affirmative vote of the holders of at least 66²/3% of the shares of American Tower Class A common stock outstanding as of the record date is required to approve the proposal to amend and restate American Tower’s certificate of incorporation.

The American Tower merger proposal is not conditioned on the proposal to amend and restate the certificate of incorporation; however, the proposal to amend and restate American Tower’s certificate of incorporation is conditioned on the consummation of the merger. Although American Tower currently has sufficient authorized shares of Class A common stock to consummate the merger, American Tower is seeking to amend and restate its certificate of incorporation to, among other things, increase the number of authorized shares. In connection with the merger, American Tower is obligated to issue up to approximately 186.5 million shares of Class A common stock, including approximately 168.2 million shares issuable at the closing with respect to outstanding shares of SpectraSite common stock as of May 20, 2005 and up to approximately 18.3 million shares issuable pursuant to outstanding SpectraSite stock options and warrants as of May 20, 2005. As a result, after consummation of the merger, American Tower would only have approximately 9.3 million authorized shares of Class A common stock that are not already issued or reserved for issuance

pursuant to outstanding options, warrants and convertible notes and its employee stock purchase plan as of May 20, 2005. The American Tower board of directors believes that it is advisable and in the best interests of the stockholders to have available additional authorized but unissued shares in an amount adequate to provide for future needs. Although American Tower currently has no specific plans to issue the additional shares that would be authorized by this proposal, other than possible future issuances pursuant to existing share reservations, these shares will provide additional flexibility to use capital stock for business and financial purposes in the future.

The proposal to amend and restate American Tower’s certificate of incorporation is conditioned on the consummation of the merger. Accordingly, if the American Tower merger proposal is not approved or the merger is not consummated for any other reason, American Tower will not amend and restate its certificate of incorporation as set forth in this joint proxy statement/prospectus, even if approved by the American Tower stockholders.

SpectraSite. The affirmative vote of the holders of a majority of the shares of SpectraSite common stock outstanding as of the record date is required to approve the SpectraSite merger proposal. The affirmative vote of the holders of a majority of shares of SpectraSite common stock voting on the proposal is required to grant discretionary authority to SpectraSite’s board of directors or its chairman to adjourn or postpone the special meeting to solicit additional votes to approve the SpectraSite merger proposal.

Conflicts of Interests of SpectraSite’s Directors and Executive Officers in the Merger (see page 63)

•

Four of SpectraSite’s current directors will become directors of American Tower;

•

SpectraSite’s executive officers will be entitled to enhanced severance pay and benefits if their employment is terminated in specified circumstances, including Stephen H. Clark, SpectraSite’s President and Chief Executive Officer, Timothy G. Biltz, SpectraSite’s Chief Operating Officer, and Mark A. Slaven, SpectraSite’s Chief Financial Officer, who will not continue as employees of American Tower after consummation of the merger;

•

The vesting of equity awards held by SpectraSite’s non-employee directors will accelerate and the vesting of equity awards granted to SpectraSite’s executive officers will accelerate in specified circumstances, including, in the case of Messrs. Clark, Blitz and Slaven, the acceleration of all unvested service options as set forth in their employment agreements; and

•

SpectraSite directors and executive officers will have the right to continued indemnification and insurance coverage by American Tower for acts and omissions occurring prior to the merger.

Board of Directors of American Tower after the Merger (see page 67)

Treatment of SpectraSite Stock Options, Warrants and Restricted Stock (see pages 65 and 66)

SpectraSite Options. All outstanding SpectraSite stock options, whether or not exercisable and whether

or not vested, will remain outstanding following the effective time of the merger. American Tower will assume the SpectraSite stock options, which shall be exercisable upon the same terms and conditions as prior to the merger, except that such options to purchase SpectraSite common stock will be exercisable for shares of American Tower Class A common stock equal to the aggregate number of shares of SpectraSite common stock subject to such SpectraSite stock option multiplied by 3.575, rounded down to the nearest whole share, and will be exercisable at an exercise price equal to the current exercise price of such SpectraSite stock option divided by 3.575.

SpectraSite Warrants. As of the effective time of the merger, the outstanding SpectraSite warrants to purchase shares of SpectraSite common stock will, in accordance with and subject to the applicable provisions of the SpectraSite warrants, remain outstanding after the effective time of the merger and be exercisable in accordance with the terms of the SpectraSite warrants, except that each SpectraSite warrant will be exercisable for that number of shares of American Tower Class A common stock equal to the aggregate shares of SpectraSite common stock subject to such SpectraSite warrant multiplied by 3.575 and will be exercisable at an exercise price equal to the current exercise price of such SpectraSite warrant divided by 3.575.

SpectraSite Restricted Stock. When the merger is consummated, each restricted share of SpectraSite common stock outstanding will be exchanged for 3.575 shares of American Tower Class A common stock and will be fully vested and will cease to be subject to any restrictions.

Regulatory Matters (see page 67)

Under U.S. antitrust laws, transactions such as the merger typically may not be consummated until the parties have notified the Antitrust Division of the Department of Justice, which we refer to as the Antitrust Division, and the Federal Trade Commission, which we refer to as the FTC, of the transaction and have made any necessary filings under and satisfied the waiting period requirements of the Hart-Scott-Rodino Antitrust Improvement Act of 1976, as amended, which we refer to as the HSR Act. The HSR Act and related regulations contain certain exceptions to the obligation to satisfy the notification and waiting period requirements. Based upon communications among American Tower, SpectraSite and the Premerger Notification Office of the FTC, the parties have concluded that consummation of the merger is not subject to the notification and waiting period requirements of the HSR Act and, therefore, no filing under the HSR Act will be made.

However, the Antitrust Division has informed American Tower and SpectraSite that it is investigating the merger and requested information and materials from American Tower and SpectraSite with respect to the merger. American Tower and SpectraSite are cooperating with the Antitrust Division to provide them the information and materials that have been requested to date. The Antitrust Division may request additional information or other materials with respect to the merger. In addition, the Antitrust Division may challenge the merger on antitrust grounds as it deems necessary or desirable in the public interest, including seeking to enjoin the merger or seeking to cause divestitures of significant assets of American Tower or SpectraSite or their respective subsidiaries. In addition, American Tower and SpectraSite may agree in connection with the Antitrust Division’s investigation of the merger to a divestiture of certain assets or to other restrictions on the conduct of its business to avoid or settle such a challenge by the Antitrust Division.

The merger agreement requires American Tower and SpectraSite to satisfy any conditions or divestiture requirements imposed upon them by regulatory authorities, if any, unless the conditions or divestitures would reasonably be expected to have a material adverse effect on the combined company.

Material U.S. Federal Income Tax Considerations of the Merger (see page 69)

Each of American Tower and SpectraSite expect the merger to qualify as a “reorganization” under Section 368(a) of the Internal Revenue Code. In general, subject to the discussion under the section captioned “MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS OF THE MERGER,”

SpectraSite stockholders will not recognize any gain or loss on the exchange of SpectraSite common stock for American Tower Class A common stock, except to the extent they receive cash in lieu of fractional shares.

Tax matters are very complicated and the tax consequences of the merger to each SpectraSite stockholder will depend on such stockholder’s particular facts and circumstances. SpectraSite stockholders are urged to consult their tax advisors to understand fully the tax consequences of the merger in their particular circumstances.

Consummation and Effectiveness of the Merger (see page 73)

The merger will become effective upon the filing of the certificate of merger with the Secretary of State of Delaware or at such other time as American Tower and SpectraSite agree and as specified in the certificate of merger. The effective time of the merger will occur as promptly as practicable, and in any event within three business days, after the satisfaction or waiver of the conditions to consummation of the merger set forth in the merger agreement. American Tower and SpectraSite hope to consummate the merger by the end of the second half of 2005.

Conditions to the Merger Agreement (see page 75)

Each of American Tower and SpectraSite is required to consummate the merger only if specific conditions set forth in the merger agreement are satisfied or waived, including the following:

•

The approval of the SpectraSite merger proposal by holders of at least a majority of the outstanding shares of SpectraSite common stock;

•

The approval of the American Tower merger proposal by the holders of at least a majority of all shares of American Tower Class A common stock casting votes at the American Tower special meeting, provided that the total votes cast represents over 50% in interest of all securities entitled to vote;

•

The absence of any applicable law or any restraining order, injunction or other judgment issued by any court or other government entity of competent jurisdiction prohibiting consummation of the merger;

•

The effectiveness of, and the absence of any stop order or proceeding seeking a stop order with respect to, the registration statement on Form S-4 of which this joint proxy statement/prospectus forms a part; and

•

The approval for listing on the NYSE, subject to official notice of issuance, of the shares of American Tower Class A common stock issuable to SpectraSite stockholders in connection with the merger.

The obligations of either American Tower or SpectraSite to effect the merger are subject to satisfaction or waiver at or prior to the closing of the merger of, among other things, American Tower having received from King & Spalding LLP, counsel to American Tower, and SpectraSite having received from Paul, Weiss, Rifkind, Wharton & Garrison LLP, counsel to SpectraSite, on the closing date of the merger, an opinion stating that the merger will be treated for U.S. federal income tax purposes as a “reorganization” within the meaning of Section 368(a) of the Internal Revenue Code and that American Tower and SpectraSite will each be a party to that reorganization within the meaning of Section 368(b) of the Internal Revenue Code.

The merger agreement also provides that the expiration or termination of any waiting period applicable to the merger under the HSR Act is a condition to the consummation of the merger. However, based upon communications among American Tower, SpectraSite and the Premerger Notification Office of the FTC, the parties have concluded that consummation of the merger is not subject to the notification and waiting period requirements of the HSR Act and, therefore, no filing under the HSR Act will be made.

“No Solicitation” Provision (see page 80)

The merger agreement contains detailed provisions prohibiting either party from seeking a competing takeover proposal.

Termination of the Merger Agreement (see page 83)

American Tower and SpectraSite can jointly agree to terminate the merger agreement at any time prior to consummation of the merger. Either company may also terminate the merger agreement if the merger is not consummated by May 3, 2006, subject to certain limitations, and under other circumstances described in this joint proxy statement/prospectus.

In addition, American Tower or SpectraSite may terminate the merger agreement to accept and enter into a binding agreement with respect to a superior proposal for an alternative business combination transaction with a third party at any time prior to obtaining the approval of the merger proposal by its stockholders.

Termination Fees and Expenses (see page 85)

Generally, all fees and expenses incurred in connection with the merger will be paid by the party incurring those fees or expenses, except that each of American Tower and SpectraSite will bear and pay one-half of certain costs and expenses as provided in the merger agreement and discussed in this joint proxy statement/prospectus.

In addition, the merger agreement provides that, in connection with a termination of the merger agreement involving certain breaches, American Tower or SpectraSite may be obligated under some circumstances to reimburse the non-breaching company’s costs up to a maximum of $10.0 million.

Further, the merger agreement provides that American Tower or SpectraSite may be required to pay a termination fee to the other equal to $110.0 million in certain circumstances involving a superior proposal for an alternative business combination transaction with a third party.

American Tower’s and SpectraSite’s obligation to pay the termination fee may discourage a third party from pursuing a competing acquisition proposal that could result in greater value to American Tower or SpectraSite stockholders. In addition, payment of the termination fee could adversely affect the financial condition of the company making the payment. The boards of directors of each of American Tower and SpectraSite determined, based in part on advice from their legal advisors, that the amount of the termination fee and the circumstances in which it would become payable were generally typical for public company merger transactions comparable to the merger and would not unduly inhibit an alternative acquisition proposal more so than is customary for comparable transactions.

Accounting Treatment (see page 68)

American Tower will account for the merger under the purchase method of accounting for business combinations.

Appraisal Rights (see page 68)

Under Delaware law, SpectraSite stockholders are not entitled to appraisal rights in connection with the merger.

SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA

The following tables present selected historical consolidated financial data of American Tower and selected historical consolidated financial data of SpectraSite.

American Tower Selected Historical Consolidated Financial Data

The following selected historical consolidated financial data is derived from American Tower’s March 31, 2005 unaudited condensed consolidated financial statements as filed in American Tower’s Quarterly Report on Form 10-Q for the three months ended March 31, 2005 and American Tower’s audited consolidated financial statements, certain of which are included in American Tower’s Annual Report on Form 10-K for the year ended December 31, 2004. In the opinion of American Tower’s management, the unaudited information described above includes all adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation. Results for the three months ended March 31, 2005 are not necessarily indicative of results for the full year.

You should read the selected historical consolidated financial data in conjunction with American Tower’s “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” audited consolidated financial statements and related notes and unaudited condensed consolidated financial statements and related notes, which are incorporated by reference into this joint proxy statement/prospectus. Year-to-year comparisons are significantly affected by the acquisition, disposition and construction of towers.


	Year Ended December 31,															Three Months Ended March 31,
	2000			2001			2002			2003			2004			2004			2005
	(In thousands, except per share data)
Statements of Operations Data:
Revenues:
Rental and management	$	269,282		$	431,051		$	544,906		$	619,697		$	684,422		$	164,576		$	181,570
Network development services		41,430			85,063			32,888			12,796			22,238			4,215			2,785

Total operating revenues		310,712			516,114			577,794			632,493			706,660			168,791			184,355

Operating expenses:
Rental and management		147,147			221,759			242,801			236,680			237,312			58,876			60,180
Network development services		33,451			69,371			29,214			9,493			18,801			3,561			2,202
Depreciation, amortization and accretion(1)		248,249			354,298			327,665			330,414			329,449			81,345			81,971
Corporate general, administrative and development expense		29,378			34,310			30,229			26,867			27,468			6,879			6,973
Impairments, net loss on sale of long-lived assets and restructuring expense					79,496			101,372			31,656			23,876			3,914			2,777

Total operating expenses		458,225			759,234			731,281			635,110			636,906			154,575			154,103

Operating (loss) income from continuing operations		(147,513	)		(243,120	)		(153,487	)		(2,617	)		69,754			14,216			30,252
Interest income, TV Azteca, net		12,679			14,377			13,938			14,222			14,316			3,540			3,498
Interest income		15,948			28,372			3,496			5,255			4,844			1,114			699
Interest expense		(151,392	)		(266,769	)		(254,345	)		(279,783	)		(262,237	)		(69,157	)		(54,716	)
Loss on retirement of long-term obligations		(24,198	)		(26,336	)		(8,869	)		(46,197	)		(138,016	)		(8,053	)		(15,042	)
Other income (expense)		926			(27,838	)		(7,004	)		(8,598	)		(2,798	)		(204	)		670

Loss from continuing operations before income taxes, minority interest and loss on equity method investments		(293,550	)		(521,314	)		(406,271	)		(317,718	)		(314,137	)		(58,544	)		(34,639	)
Income tax benefit		84,107			115,841			81,141			77,796			80,176			13,018			4,338
Minority interest in net earnings of subsidiaries		(202	)		(318	)		(2,118	)		(3,703	)		(2,366	)		(1,423	)		(55	)
Loss on equity method of investments		(3,391	)		(10,957	)		(18,555	)		(21,221	)		(2,915	)		(618	)		(1,098	)

Loss from continuing operations before cumulative effect of change in accounting principle	$	(213,036	)	$	(416,748	)	$	(345,803	)	$	(264,846	)	$	(239,242	)	$	(47,567	)	$	(31,454	)

Basic and diluted loss per common share from continuing operations before cumulative effect of change in accounting principle	$	(1.26	)	$	(2.18	)	$	(1.77	)	$	(1.27	)	$	(1.07	)	$	(0.22	)	$	(0.14	)

Weighted average common shares outstanding(2)		168,715			191,586			195,454			208,098			224,336			220,408			230,158


	As of December 31,										As of March 31, 2005
	2000		2001		2002		2003		2004		As of March 31, 2005
	(In thousands)
Balance Sheet Data:
Cash and cash equivalents (including restricted cash and investments)(3)	$	128,074	$	130,029	$	127,292	$	275,501	$	215,557	$	122,797
Property and equipment, net		2,278,940		3,254,905		2,650,490		2,483,324		2,273,356		2,231,278
Total assets		5,642,546		6,801,483		5,628,317		5,290,654		5,085,972		4,924,900
Long-term obligations, including current portion		2,468,223		3,561,960		3,448,514		3,359,731		3,293,614		3,147,185
Total stockholders’ equity		2,841,169		2,811,392		1,660,858		1,610,178		1,470,953		1,452,331

(1)

As of January 1, 2002, American Tower adopted the provisions of SFAS No. 142, “Goodwill and Other Intangible Assets,” (SFAS No. 142). Accordingly, American Tower ceased amortizing goodwill on January 1, 2002. The statements of operations for all periods presented, except for the years ended December 31, 2000 and 2001 do not include goodwill amortization. The adoption of SFAS No. 142 reduced amortization expense in continuing operations by approximately $67.6 million per year.

(2)

American Tower computed basic and diluted loss per common share from continuing operations before cumulative effect of change in accounting principle using the weighted average number of shares outstanding during each period presented. American Tower has excluded shares issuable upon exercise of options and other common stock equivalents from these computations, as their effect is anti-dilutive.

(3)

Includes, as of December 31, 2000 and 2001, approximately $46.0 million and $94.1 million, respectively, of restricted funds required under American Tower’s previous credit facility to be held in escrow. Includes, as of December 31, 2003, approximately $170.0 million of restricted funds that were held in escrow to pay, repurchase, redeem or retire certain of American Tower’s outstanding debt through January 2004. As of December 31, 2004 and March 31, 2005, no escrows are required under the terms of American Tower’s credit facility.

SpectraSite Selected Historical Consolidated Financial Data

The following table sets forth selected historical consolidated financial data of SpectraSite. SpectraSite refers to the periods prior to SpectraSite’s emergence from chapter 11 as “predecessor company” and to the periods subsequent to that date as “reorganized company.” The balance sheet data as of December 31, 2000, 2001, 2002 and the statement of operations data for the years ended December 31, 2000, 2001 and 2002, for the predecessor company, are derived from SpectraSite’s audited consolidated financial statements. The balance sheet data as of December 31, 2003 and 2004 and the statement of operations data for the eleven months ended December 31, 2003 and the year ended December 31, 2004, for the reorganized company, are also derived from SpectraSite’s audited consolidated financial statements. The balance sheet data as of January 31, 2003, March 31, 2004 and March 31, 2005, for the reorganized company, and the statement of operations data for the one month ended January 31, 2003, for the predecessor company, and for the three months ended March 31, 2004 and March 31, 2005, for the reorganized company, are derived from SpectraSite’s unaudited financial statements. In SpectraSite’s opinion, the unaudited financial data include all adjustments (consisting only of normal recurring adjustments and fresh start accounting adjustments for the predecessor company for the one month ended January 31, 2003 and normal recurring adjustments for the reorganized company for the three months ended March 31, 2004 and March 31, 2005), necessary to present fairly the information set forth therein. Results for the three months ended March 31, 2005 are not necessarily indicative of results for the full year.

On December 31, 2002, SpectraSite sold its network services division. On December 16, 2003, SpectraSite decided to discontinue its broadcast services division and on March 1, 2004, the division was sold. The results of the network and broadcast services divisions’ operations have been reported separately as discontinued operations in the balance sheets and statements of operations. Prior period information has been restated to present the operations of the network and broadcast services divisions as discontinued operations.

As a result of the implementation of fresh start accounting as of January 31, 2003, SpectraSite’s financial statements after that date are not comparable to SpectraSite’s financial statements for prior periods because of the differences in the bases of accounting and the capital structure for the predecessor company and the reorganized company.

The information set forth below should be read in conjunction with SpectraSite’s “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and consolidated financial statements and related notes, which are set forth in SpectraSite’s Annual Report on Form 10-K for the year ended December 31, 2004 and the unaudited condensed consolidated financial statements and related notes, which are set forth in SpectraSite’s Quarterly Report on Form 10-Q for the period ended March 31, 2005, and in each case, incorporated by reference into this joint proxy statement/prospectus. See the section captioned “WHERE YOU CAN FIND MORE INFORMATION” beginning on page 114.


	Predecessor Company(1)												Reorganized Company
	Year Ended December 31,									One Month Ended January 31, 2003(2)(3)			Eleven Months Ended December 31, 2003(1)(2)			Year Ended December 31, 2004		Three Months Ended March 31, 2004		Three Months Ended March 31, 2005
	2000			2001			2002			One Month Ended January 31, 2003(2)(3)			Eleven Months Ended December 31, 2003(1)(2)			Year Ended December 31, 2004		Three Months Ended March 31, 2004		Three Months Ended March 31, 2005
	(Dollars in thousands, except per share amounts)
Statement of Operations Data:
Revenues	$	117,970		$	221,735		$	282,525		$	25,626		$	289,713		$	355,148	$	84,740	$	93,816

Operating expenses:
Costs of operations (excluding depreciation, amortization and accretion expenses)		46,667			91,694			108,540			8,901			113,725			123,801		30,393		31,508
Selling, general and administrative expenses		42,977			65,540			54,812			4,003			45,822			53,199		12,042		15,170
Depreciation, amortization and accretion expenses(4)		76,986			163,628			188,176			15,930			104,843			117,503		29,188		30,587
Restructuring and non-recurring charges					140,871			27,394

Total operating expenses		166,630			461,733			378,922			28,834			264,390			294,503		71,623		77,265

Operating (loss) income		(48,660	)		(239,998	)		(96,397	)		(3,208	)		25,323			60,645		13,117		16,551

Gain on debt discharge											1,034,764
(Loss) income from continuing operations	$	(163,812	)	$	(658,935	)	$	(338,558	)	$	1,026,474		$	(29,539	)	$	23,926	$	1,119	$	11,632

(Loss) income from continuing operations per common share—basic	$	(1.36	)	$	(4.39	)	$	(2.20	)	$	6.66		$	(0.62	)	$	0.50	$	0.02	$	0.25

(Loss) income from continuing operations per common share—diluted	$	(1.36	)	$	(4.39	)	$	(2.20	)	$	6.66		$	(0.62	)	$	0.46	$	0.02	$	0.23

Weighted average common shares outstanding—basic		120,731			150,223			153,924			154,014			47,406			48,149		47,880		46,686
Weighted average common shares outstanding—diluted		120,731			150,223			153,924			154,014			47,406			51,957		52,368		50,363

Balance Sheet Data (at end of period):
Cash and cash equivalents	$	552,653		$	31,547		$	80,961		$	73,442		$	60,410		$	34,649	$	84,329	$	69,709
Total assets	$	3,054,105		$	3,203,425		$	2,578,456		$	2,577,575		$	1,502,143		$	1,431,072	$	1,503,204	$	1,450,473
Total long-term obligations	$	1,708,273		$	2,326,012		$	791,992		$	849,240		$	696,179		$	825,107	$	700,999	$	829,407
Total stockholders’ equity (deficit)	$	1,224,800		$	719,345		$	(75,127	)	$	(96,678	)	$	640,320		$	497,319	$	645,782	$	510,027

(1)

On February 10, 2003, SpectraSite emerged from chapter 11. In accordance with AICPA Statement of Position 90-7 Financial Reporting by Entities in Reorganization Under the Bankruptcy Code (“SOP 90-7”), SpectraSite adopted fresh start accounting as of January 31, 2003 and SpectraSite’s emergence from chapter 11 resulted in a new reporting entity. Under fresh start accounting, the reorganization value of the entity is allocated to the entity’s assets based on fair values, and liabilities are stated at the present value of amounts to be paid determined at appropriate current interest rates. The net effect of all fresh start accounting adjustments resulted in a charge of $644.7 million, which is reflected in the statement of operations for the one month ended January 31, 2003. The effective date is considered to be the close of business on January 31, 2003 for financial reporting purposes. The periods presented prior to January 31, 2003 have been designated “predecessor company” and the periods subsequent to January 31, 2003 have been designated “reorganized company.” As a result of the implementation of fresh start accounting as of January 31, 2003, SpectraSite’s financial statements after the effective date are not comparable to SpectraSite’s financial statements for prior periods because of differences in the bases of accounting and the capital structure for the predecessor company and the reorganized company.

(2)

On February 10, 2003, SpectraSite sold 545 SBC towers to Cingular Wireless. See SpectraSite’s “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Tower Acquisitions and Dispositions” which is set forth in SpectraSite’s Annual Report on Form 10-K for the year ended December 31, 2004 for a discussion of the impact of the sale of these towers on SpectraSite’s results of operations and financial position.

(3)	Selected balance sheet data as of January 31, 2003 for the predecessor company is unaudited.

(4)	Depreciation, amortization and accretion expenses for the one-month and eleven-month periods are not proportional because the predecessor company and the reorganized company used different bases of accounting.

SELECTED UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL DATA

The following selected unaudited pro forma condensed combined financial data has been prepared to give effect to the merger using the purchase method of accounting, and is based upon the assumptions and adjustments described in the notes to the unaudited pro forma condensed combined financial information included elsewhere in this joint proxy statement/prospectus. This selected unaudited pro forma condensed combined financial data was prepared as if the merger had been consummated on January 1, 2004 for statements of operations purposes and on March 31, 2005 for balance sheet purposes.

The selected unaudited pro forma condensed combined financial data is presented for illustrative purposes only and is not necessarily indicative of the financial position or results of operations that would have actually been reported had the proposed transaction occurred on the dates indicated, nor is it necessarily indicative of the future financial position or results of operations of the combined company.

The selected unaudited pro forma condensed combined financial data is based upon, and should be read in conjunction with, the historical consolidated financial statements of American Tower and SpectraSite and related notes incorporated by reference herein and contained in the reports and other information American Tower and SpectraSite have filed with the SEC. See the section captioned “UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION” beginning on page 94 for a description of the accounting treatment of the proposed transaction, the Unaudited Pro Forma Combined Balance Sheet and Notes thereto, the Unaudited Pro Forma Combined Statements of Operations, and unaudited pro forma adjustments to the historical financial information of American Tower and SpectraSite showing the effects of the merger.


	Year Ended December 31, 2004			Three Months Ended March 31, 2005
Statement of Operations Data:	(In thousands, except per share data)
Revenues	$	1,061,808		$	278,171
Loss from continuing operations	$	(266,765	)	$	(32,816	)
Loss from continuing operations per common share—basic and diluted	$	(0.68	)	$	(0.08	)
Weighted average shares outstanding—basic and diluted		392,118			397,940


	As of March 31, 2005
Balance Sheet Data:	(In thousands)
Current assets	$	292,727
Current liabilities		314,003
Property and equipment, net		3,930,346
Total assets		9,081,271
Long-term obligations, including current portion		3,906,437
Stockholders’ equity		4,607,628

UNAUDITED COMPARATIVE PER SHARE DATA

Presented below is per share data regarding the income and book value of American Tower and SpectraSite on both a historical and a per share equivalent unaudited pro forma basis. The unaudited pro forma combined per share information is based upon the unaudited pro forma condensed combined financial information included elsewhere in this joint proxy statement/prospectus. You should read the information below in conjunction with the financial statements and accompanying notes of each of American Tower and SpectraSite incorporated by reference herein and with the unaudited pro forma condensed combined financial information included herein. The American Tower unaudited pro forma combined per share information is calculated by combining the American Tower historical share amounts with pro forma share amounts of SpectraSite, based on the SpectraSite historical share amounts and the exchange ratio of 3.575 shares of American Tower Class A common stock for each share of SpectraSite common stock. The SpectraSite unaudited pro forma equivalent per share information is calculated by multiplying the actual American Tower unaudited pro forma combined per share information by the exchange ratio of 3.575. These amounts do not necessarily reflect future per share amounts of income (loss) from continuing operations and book value per share of American Tower.


	As of and for the Year Ended December 31, 2004			As of and for the Three Months Ended March 31, 2005
American Tower Historical Per Common Share:
Loss from continuing operations per common share—basic and diluted	$	(1.07	)	$	(0.14	)
Book value per share		6.41			6.30
Cash dividends		N/A			N/A

SpectraSite Historical Per Common Share:
Income from continuing operations per common share—basic	$	0.50		$	0.25
Income from continuing operations per common share—diluted		0.46			0.23
Book value per share		10.80			10.88
Cash dividends		N/A			N/A

American Tower Unaudited Pro Forma Combined Per Common Share:
Loss from continuing operations per common share—basic and diluted	$	(0.68	)	$	(0.08	)
Book value per common share		—			11.57
Cash dividends		N/A			N/A

SpectraSite Unaudited Pro Forma Equivalent Per Common Share:
Loss from continuing operations per common share—basic and diluted	$	(2.43	)	$	(0.29	)
Book value per common share		—			41.36
Cash dividends		N/A			N/A

COMPARATIVE PER SHARE MARKET PRICE DATA AND DIVIDEND INFORMATION

American Tower Class A common stock trades on the NYSE under the symbol “AMT.” SpectraSite common stock began trading on the NYSE under the symbol “SSI” on October 3, 2003. SpectraSite common stock previously traded on the Pink Sheets and on the OTC Bulletin Board. The table below sets forth, for the periods indicated, the high and low per share sales prices for American Tower Class A common stock and SpectraSite common stock, as adjusted to reflect the 2-for-1 split of SpectraSite common stock effective August 21, 2003, in each case, as reported on the NYSE, OTC Bulletin Board or Pink Sheets, as applicable. During the periods presented neither American Tower nor SpectraSite declared any cash dividends.


	American Tower Class A Common Stock				SpectraSite Common Stock
	High		Low		High		Low
Calendar Year 2003
First Quarter (beginning February 11, 2003 for SpectraSite)	$	5.94	$	3.55	$	16.00	$	12.25
Second Quarter		9.90		5.41		27.05		14.00
Third Quarter		11.74		8.73		34.50		24.88
Fourth Quarter		12.00		9.59		39.30		30.00

Calendar Year 2004
First Quarter	$	13.12	$	9.89	$	39.80	$	33.50
Second Quarter		16.00		11.13		44.20		35.60
Third Quarter		15.85		13.10		46.95		40.32
Fourth Quarter		18.75		15.19		59.65		46.16

Calendar Year 2005
First Quarter	$	19.28	$	17.30	$	63.99	$	55.05
Second Quarter (through May 20, 2005)		18.52		16.28		62.65		53.41

The above table shows only historical comparisons. Because the market prices of American Tower Class A common stock and SpectraSite common stock will fluctuate prior to the merger, these comparisons may not provide meaningful information to American Tower stockholders in determining whether to approve the American Tower merger proposal or to SpectraSite stockholders in determining whether to approve the SpectraSite merger proposal. American Tower and SpectraSite stockholders are encouraged to obtain current market quotations for American Tower and SpectraSite common stock and to review carefully the other information contained in this joint proxy statement/prospectus or incorporated by reference into this joint proxy statement/prospectus in considering whether to approve their respective proposals. See the section captioned “WHERE YOU CAN FIND MORE INFORMATION” beginning on page 114.

The table below sets forth for May 3, 2005, the last trading day before American Tower and SpectraSite announced the merger, and [·], 2005, the last trading day before the date of this joint proxy statement/prospectus, the closing prices for American Tower Class A common stock and SpectraSite common stock as reported on the NYSE, as well as the pro forma equivalent per share value of SpectraSite common stock based on the exchange ratio of 3.575 shares of American Tower Class A common stock for each outstanding share of SpectraSite common stock.

American Tower
Common Stock

SpectraSite
Common Stock

Pro Forma Equivalent of
SpectraSite

Common Stock

May 3, 2005

17.21

56.20

61.53

[·], 2005

[

·]

[

·]

[

·]

RISK FACTORS

Before you vote, you should carefully consider the risks described below in addition to the other information contained in or incorporated by reference into this joint proxy statement/prospectus, including matters addressed in the section captioned “STATEMENT REGARDING FORWARD-LOOKING INFORMATION” beginning on page 116. The risks and uncertainties described below are not the only ones facing American Tower, SpectraSite and the combined company. Additional risks and uncertainties not presently known to either of American Tower or SpectraSite or that we believe are now immaterial may also impair American Tower’s or SpectraSite’s business. If any of the following risks actually occur, the business, financial condition or results of operations of American Tower, SpectraSite or the combined company could be materially adversely affected, the value of American Tower Class A common stock or SpectraSite common stock could decline and American Tower stockholders and SpectraSite stockholders may lose all or part of their investment. You should also carefully consider the risks described in the documents incorporated by reference in this joint proxy statement/prospectus. See the section captioned “WHERE YOU CAN FIND MORE INFORMATION” beginning on page 114.

Risks Associated with the Merger

The exchange ratio set forth in the merger agreement is fixed and will not be adjusted in the event of any change in American Tower’s or SpectraSite’s market price.

As a result of the merger, each share of SpectraSite common stock outstanding at the effective time of the merger will be converted automatically into the right to receive 3.575 shares of American Tower Class A common stock. The ratio at which shares of SpectraSite common stock will be converted is fixed in the merger agreement and the merger agreement does not provide for any adjustment for changes in the market price of either SpectraSite common stock or American Tower Class A common stock. Any change in the market price of American Tower Class A common stock will affect the market value of the shares that SpectraSite stockholders receive in the merger.

•

If the market price of American Tower Class A common stock declines before the effective time of the merger, SpectraSite stockholders will receive shares having less market value for their shares of SpectraSite common stock.

If the market price of American Tower Class A common stock declines between the date the merger agreement was signed or the date of the SpectraSite special meeting and the effective time of the merger, including for any of the reasons described in the third bullet of this risk factor, SpectraSite stockholders will receive shares having a lower market value for their shares upon consummation of the merger than they would have received based on the value calculated pursuant to the exchange ratio on the date the merger agreement was signed or on the date of the SpectraSite special meeting.

•

If the market price of American Tower Class A common stock increases before the effective time of the merger, American Tower will pay SpectraSite stockholders a greater amount of value for their shares of SpectraSite common stock.

If the market price of American Tower Class A common stock increases between the date the merger agreement was signed or the date of the American Tower special meeting and the effective time of the merger, the market value of the shares that American Tower will pay to SpectraSite stockholders will be greater than the market value calculated pursuant to the exchange ratio on the date the merger agreement was signed or on the date of the American Tower special meeting.

•

The market price of American Tower Class A common stock will fluctuate.

The market price of American Tower Class A common stock has fluctuated and will fluctuate between the date of this joint proxy statement/prospectus and the effective time of the merger. For example, from May 20, 2004 to May 20, 2005, the sale price of American Tower Class A common stock ranged from a

low of $12.92 per share to a high of $19.28 per share, as reported on the NYSE. See the section captioned “COMPARATIVE PER SHARE MARKET PRICE DATA AND DIVIDEND INFORMATION” beginning on page 15. Further variations in the market price of American Tower Class A common stock could be the result of changes in the actual or perceived business, operations or prospects of American Tower, SpectraSite or the combined company, market assessments of the likelihood that the merger will be consummated or the timing of the consummation of the merger, regulatory considerations, general market and economic conditions and other factors both within and beyond the control of American Tower or SpectraSite. Neither American Tower nor SpectraSite is permitted to “walk away” from or terminate the merger or resolicit the vote of its stockholders solely because of changes in the market price of either party’s common stock. Because the date that the merger is consummated will be later than the date of the SpectraSite and American Tower special meetings, at the time of the special meetings you will not know the market value of the American Tower Class A common stock that SpectraSite stockholders will receive upon consummation of the merger.

The merger is subject to the receipt of consents and approvals from, or challenge by, various government entities, which may impose conditions on, jeopardize or delay consummation of the merger or reduce the anticipated benefits of the merger.

Consummation of the merger is conditioned upon filings with, and the receipt of required consents, orders, approvals or clearances from, various governmental agencies, including, without limitation, the FTC and the Antitrust Division. Although American Tower and SpectraSite have concluded that consummation of the merger is not subject to the notification and waiting period requirements of the HSR Act and no filing under the HSR Act will be made, the Antitrust Division has informed American Tower and SpectraSite that it is investigating the merger and requested information and materials from American Tower and SpectraSite with respect to the merger. There is no assurance that the Antitrust Division will not challenge the merger on antitrust grounds seeking to enjoin the merger or seeking to cause divestitures of significant assets of American Tower or SpectraSite or their respective subsidiaries or that, if a challenge is made, American Tower and SpectraSite will prevail. Additionally, at any time before or after the consummation of the merger, any state or foreign governmental entity could take action under the antitrust laws as it deems necessary or desirable in the public interest, or other persons can take action under the antitrust laws. There is no assurance that all of these required consents, orders, approvals and clearances will be obtained, and if they are obtained, they may not be obtained before American Tower and SpectraSite stockholders vote on the merger.

Moreover, even if the required consents, orders, approvals and clearances are obtained, they may impose conditions on, or require divestitures relating to, the operations or assets of American Tower or SpectraSite. These conditions or required divestitures may jeopardize or delay consummation of the merger or reduce the anticipated benefits of the merger. The merger agreement requires each of American Tower and SpectraSite to use its reasonable best efforts to satisfy any conditions or divestiture requirements imposed upon them unless the conditions or divestitures would reasonably be expected to have, individually or in the aggregate, a material adverse effect on the combined company.

Any of the conditions or restrictions imposed by a regulatory authority may result in the merger being consummated on terms different from those described in this joint proxy statement/prospectus and, as a result, the benefits of the merger may be different from those described in this joint proxy statement/prospectus. These conditions or restrictions may jeopardize or delay the closing of the merger or may reduce the anticipated benefits of the merger. Any delay could, among other things, result in additional transaction costs, loss of revenue or other negative effects associated with uncertainty about the closing of the merger.

The merger is subject to certain conditions to closing that could result in the merger being delayed or not consummated, which could negatively impact American Tower’s or SpectraSite’s stock price and future business and operations.

Failure to consummate the merger could negatively impact American Tower’s or SpectraSite’s stock price and future business and operations. The merger is subject to customary conditions to closing, as set forth in the merger agreement. If any of the conditions to the merger are not satisfied or, where waiver is permissible, not waived, the merger will not be consummated. Any delay in the consummation of the merger or any uncertainty about the consummation of the merger could adversely affect the future businesses, growth, revenue and results of operations of either or both of the companies or the combined company. American Tower and SpectraSite cannot assure their stockholders that the merger will be consummated, that there will not be a delay in the consummation of the merger, that the merger will be consummated on the terms contemplated by the merger agreement and as described in this joint proxy statement/prospectus or that the benefits of the merger will be the same as those described in this joint proxy statement/prospectus.

Whether or not the merger is consummated, the announcement and pendency of the merger could cause disruptions in the businesses of American Tower and SpectraSite, which could have an adverse effect on their business and financial results.

Whether or not the merger is consummated, the announcement and pendency of the merger could cause disruptions in or otherwise negatively impact the businesses of American Tower or SpectraSite. Specifically:

•

the business combination of American Tower and SpectraSite may disrupt the respective companies’ business relationships with current customers. For example, a customer may delay or defer decisions about current and future agreements with American Tower and SpectraSite because of the pending merger;

•

current and prospective employees of American Tower and SpectraSite may experience uncertainty about their future roles with the combined company, which might adversely affect American Tower’s and SpectraSite’s ability to retain key managers and other employees; and

•

the attention of management of each of American Tower and SpectraSite may be directed from business operations toward the consummation of the merger.

These disruptions could be exacerbated by a delay in the consummation of the merger or termination of the merger agreement and could have an adverse effect on the businesses and financial results of American Tower and SpectraSite if the merger is not consummated or of the combined company if the merger is consummated.

Certain directors and executive officers of SpectraSite have interests that are different from, or in addition to, interests of SpectraSite stockholders generally.

When considering the recommendation of the SpectraSite board of directors with respect to the SpectraSite merger proposal, the SpectraSite stockholders should be aware that some directors and executive officers of SpectraSite have interests in the merger that are different from, or are in addition to, the interests of the SpectraSite stockholders. Specifically, four directors of SpectraSite, including Messrs. Clark and Biltz, will become directors of American Tower upon consummation of the merger. American Tower will indemnify and maintain liability insurance for these individuals and members of the SpectraSite board of directors for their services as directors prior to the merger. Furthermore, the consummation of the merger will result in the accelerated vesting of equity-based awards held by SpectraSite’s non-employee directors and will also result in the accelerated vesting of equity-based awards held by executive officers in specified circumstances and the payment of enhanced severance pay and benefits to executive officers upon their termination of employment in specified circumstances, including Messrs. Clark, Biltz and Slaven, who will not continue as employees of American Tower after consummation of the merger. As a result, these directors and officers may be more likely to vote for the SpectraSite merger proposal than if they did not have these other interests. As of the record date,

directors and executive officers of SpectraSite beneficially owned [·] shares of SpectraSite common stock, or approximately [·]% of the shares of SpectraSite common stock outstanding on that date. Stockholders should consider these interests in conjunction with the recommendation of the boards of directors of American Tower and SpectraSite approving the proposals related to the merger. See the section captioned “PROPOSAL NUMBER ONE: THE MERGER PROPOSALS—Conflicts of Interests of SpectraSite Directors and Executive Officers in the Merger” beginning on page 63.

American Tower and SpectraSite will incur significant costs associated with the merger whether or not the merger is consummated.

American Tower and SpectraSite will incur significant costs related to the merger, including legal, accounting, advisory, filing and printing fees. Some of these costs will be incurred whether or not the merger is consummated. If the merger agreement is terminated under specified circumstances, American Tower or SpectraSite may be obligated to pay the other party a $110.0 million termination fee. In connection with a termination of the merger agreement involving certain breaches, American Tower or SpectraSite may be obligated under some circumstances to reimburse the non-breaching company’s costs up to a maximum of $10.0 million. See the section captioned “THE MERGER AGREEMENT—Expenses and Termination Fees” beginning on page 85.

The merger agreement limits American Tower’s and SpectraSite’s ability to pursue an alternative transaction proposal to the merger and requires American Tower or SpectraSite to pay a termination fee if it does.

The merger agreement prohibits American Tower and SpectraSite from soliciting, initiating, encouraging or facilitating certain alternative transaction proposals with any third party, subject to exceptions set forth in the merger agreement. See the section captioned “THE MERGER AGREEMENT—No Solicitation” beginning on page 80. Further, the merger agreement provides that American Tower or SpectraSite may be required to pay a termination fee to the other equal to $110.0 million in certain circumstances involving a superior proposal with respect to an alternative business combination transaction with a third party. See the section captioned “THE MERGER AGREEMENT—Expenses and Termination Fees” beginning on page 85. These provisions limit American Tower’s and SpectraSite’s ability to pursue offers from third parties that could result in greater value to American Tower’s or SpectraSite’s stockholders relative to the terms and conditions of the merger. American Tower’s and SpectraSite’s obligation to pay the termination fee may discourage a third party from pursuing a competing acquisition proposal that could result in greater value to American Tower or SpectraSite stockholders. In addition, payment of the termination fee could adversely affect the financial condition of the company making the payment.

Further, if the merger agreement is terminated and the board of directors of either American Tower or SpectraSite determines to seek another merger or business combination, it may not be able to find a partner willing to provide an equivalent or more attractive benefit to the applicable company’s stockholders than that which would have been obtained by such stockholders in the merger.

Risks Associated with American Tower Following the Merger

American Tower and SpectraSite may not realize the intended benefits of the merger if American Tower is unable to integrate SpectraSite’s operations, wireless communications tower portfolio and personnel in a timely and efficient manner, which could adversely affect the value of American Tower Class A common stock following the merger.

Achieving the benefits of the merger will depend in part on the integration of American Tower’s and SpectraSite’s operations, wireless communications tower portfolios and personnel in a timely and efficient manner and the ability of the combined company to realize the anticipated synergies from this integration. American Tower and SpectraSite will continue to operate independently until the consummation of the merger.

This integration may be difficult and unpredictable for many reasons, including, among others, the size of SpectraSite’s wireless communications tower portfolio and because SpectraSite’s and American Tower’s internal systems and processes were developed without regard to such integration. Successful integration of American Tower and SpectraSite also requires coordination of different personnel, which may be difficult and unpredictable because of possible cultural conflicts and differences in policies, procedures and operations between the companies and the different geographical locations of the companies. If American Tower cannot successfully integrate SpectraSite’s operations, wireless communications tower portfolio and personnel, American Tower and SpectraSite may not realize the expected benefits of the merger, which could adversely affect the combined company’s business and could adversely affect the value of American Tower Class A common stock after the merger. In addition, the integration of American Tower’s and SpectraSite’s businesses may place a significant burden on management and its internal resources. The diversion of management’s attention from ongoing business concerns and any difficulties encountered in the transition and integration process could harm the combined company’s business and the value of American Tower Class A common stock.

American Tower is expected to incur substantial expenses related to the integration of SpectraSite.

American Tower is expected to incur substantial expenses in connection with the integration of the business, policies, procedures, operations and systems of SpectraSite with those of American Tower. The failure of the combined company to meet the challenges involved in integrating the companies’ business and operations, or to do so in a timely basis, could cause substantial additional expenses and serious harm to the combined company. For example, there are a large number of systems that must be integrated, including management information, accounting and finance, sales, billing, payroll and benefits, lease administration systems and regulatory compliance. While American Tower has assumed that a certain level of expenses would be incurred, there are a number of factors, some of which are beyond its control, that could affect the total amount or the timing of all of the expected integration expenses including:

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constraints arising under U.S. federal or state antitrust laws, such as limitations on sharing of information, that may prevent or hinder American Tower from fully developing integration plans;

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employee redeployment, relocation or severance, as well as reorganization or closures of facilities;

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consolidating and rationalizing information technology and administrative infrastructures;

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consolidating operation and management of combined tower portfolio;

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coordinating sales and marketing efforts to effectively communicate the capabilities of the combined company;

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preserving supply, marketing or other important relationships of both American Tower and SpectraSite and resolving potential conflicts that may arise; and

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minimizing the diversion of management’s attention from ongoing business concerns and successfully returning managers to regular business responsibilities from their integration planning activities.

Many of the expenses that will be incurred, by their nature, are impracticable to estimate at the present time. These expenses could, particularly in the near term, exceed the savings that the combined company expects to achieve from the elimination of duplicative expenses and the realization of economies of scale and cost savings related to the integration of the businesses following the consummation of the merger.

The combined company’s revenue will be further dependant upon and derived from a small number of customers.

Due to the overlap in customers of American Tower and SpectraSite and the consolidation of wireless carriers in general, a substantial portion of the combined company’s total operating revenues will continue to be derived from a small number of customers. For the year ended December 31, 2004, on a pro forma basis after giving effect to the merger and the industry transactions described below:

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Approximately 59% of the combined company’s revenues would be derived from six customers;

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Approximately 21% of the combined company’s revenues would be derived from Cingular Wireless, which merged with AT&T Wireless in October 2004;

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Approximately 17% of the combined company’s revenues would be derived from Sprint PCS and Nextel, which announced their merger plans in December 2004; and

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Approximately 10% of the combined company’s revenues would be derived from Verizon Wireless.

If any of these customers were unwilling or unable to perform their obligations under any agreements with the combined company, the combined company’s revenues, results of operations, and financial condition could be adversely affected. In the ordinary course of business, American Tower and SpectraSite also sometimes experience disputes with their customers, generally regarding the interpretation of terms in their respective agreements. Although historically American Tower and SpectraSite resolved these disputes in a manner that did not have a material adverse effect on their respective businesses or customer relationships, in the future these disputes could lead to a termination of agreements with customers or a material modification of the terms of those agreements, either of which could have a material adverse effect on the combined company’s business, results of operations and financial condition. If the combined company is forced to resolve any of these disputes through litigation, the combined company’s relationship with the applicable customer could be terminated or damaged, which could lead to decreased revenues or increased costs, resulting in a corresponding adverse effect on the combined company’s business, results of operations and financial condition.

Following the consummation of the merger, the combined company’s leverage will be substantially higher than SpectraSite’s current leverage, and the combined company’s indebtedness will be greater than either company’s existing indebtedness.

After giving effect to the merger, the combined company’s leverage will be significantly greater than the leverage of SpectraSite prior to the merger. Therefore, upon consummation of the merger, SpectraSite stockholders, as stockholders of the combined company, will hold interests in a company with higher leverage than prior to the merger. As a consequence of American Tower’s greater indebtedness, the combined company will be subject to restrictive covenants that will further limit the financial and operating flexibility of the combined company. The covenants contained in American Tower’s and SpectraSite’s credit facilities and American Tower’s and SpectraSite’s indentures could place the combined company at a disadvantage compared to some of its competitors which may have fewer restrictive covenants and may not be required to operate under these restrictions. For example, the limits imposed by American Tower’s and SpectraSite’s indebtedness restrict their ability to take various actions, including incurring additional debt, guaranteeing indebtedness, issuing preferred stock, engaging in various types of transactions, including mergers and sales of assets, and paying dividends and making distributions or other restricted payments, including investments. These restrictions could have an adverse effect on the business of the combined company by limiting its ability to take advantage of financing, new tower development, merger and acquisition or other opportunities.

The indebtedness of SpectraSite as of March 31, 2005 was approximately $749.0 million, and the indebtedness of American Tower as of March 31, 2005 was approximately $3.1 billion. American Tower’s pro forma indebtedness as of March 31, 2005, giving effect to the merger, as described in the section captioned “UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION” beginning on page 94, would have been approximately $3.9 billion. As a result of the contemplated increase in debt, demands on American Tower’s cash resources will increase after the merger, which could negatively impact the business, results of operations and financial condition of the combined company and the market price of American Tower Class A common stock. For example, while the impact of this increased indebtedness will be addressed by the combined cash flows of American Tower and SpectraSite, the increased levels of indebtedness could nonetheless reduce funds available to American Tower for tower acquisitions, construction and improvements, or create competitive disadvantages for American Tower compared to other companies with lower debt levels.

As a result of the merger, the combined company may need to repay or redeem SpectraSite’s current indebtedness, and additional funds necessary to finance that repayment or redemption may not be available on terms favorable to the combined company, if at all.

As a result of the merger, the combined company may be required to make an offer to repurchase SpectraSite’s 8.25% senior notes due 2010 at a price equal to 101% of the aggregate principal amount of the notes outstanding, plus accrued and unpaid interest. If SpectraSite’s senior notes receive a ratings decline by either Standard & Poor’s Rating Services or Moody’s Investor’s Service, Inc. within 90 days from public announcement of the proposed merger, which time period may be extended so long as the rating of the senior notes is under publicly announced consideration for downgrade by either rating agency, the combined company will be required to make an offer to repurchase the senior notes, unless American Tower obtains the necessary consents, amendments or waivers under the related indenture, including an amendment to the definition of the term “change of control” to exclude the transactions contemplated by the merger agreement.

As of May 20, 2005, SpectraSite’s senior notes were rated B- by Standard & Poor’s and B2 by Moody’s. As of March 31, 2005, SpectraSite had $200.0 million aggregate principal amount of the senior notes outstanding.

In addition, the combined company may be required to refinance or replace the $900.0 million senior secured credit facility of SpectraSite Communications, Inc., a wholly owned subsidiary of SpectraSite, unless the combined company obtains necessary consents, amendments or waivers under the credit agreement governing the credit facility, including an amendment to the definition of the term “change of control” to exclude the transactions contemplated by the merger agreement. As of March 31, 2005, the aggregate amount outstanding under the credit facility was approximately $549.0 million.

If necessary, American Tower and SpectraSite expect that the combined company will finance any required repurchase of SpectraSite’s senior notes from the incurrence of additional indebtedness and any refinancing or replacement of SpectraSite’s credit facility with a substitute credit facility that is, to the extent available, on substantially similar terms. However, neither the repurchase of SpectraSite’s senior notes nor the refinancing of SpectraSite’s credit facility is a condition to the consummation of the merger. Neither American Tower nor SpectraSite can assure you, however, that the combined company will be able to obtain the financing necessary to repurchase SpectraSite’s senior notes and refinance or replace SpectraSite’s credit facility on terms favorable to it, if at all. If the combined company is unable to obtain necessary financing on favorable terms, the earnings and cash flow of the combined company could be materially adversely affected. If the combined company is unable to obtain the necessary financing to repurchase SpectraSite’s senior notes or to refinance or replace SpectraSite’s credit facility, it would be in default under SpectraSite’s senior notes indenture or SpectraSite’s credit facility, respectively. An acceleration of the indebtedness evidenced by SpectraSite’s senior notes would cause a cross-acceleration of amounts owing under SpectraSite’s credit facility, and vice-versa.

If the merger is consummated but the proposal to amend and restate American Tower’s certificate of incorporation is not approved, the ability of American Tower to issue additional shares of American Tower Class A common stock would be limited.

The American Tower merger proposal is not conditioned on the proposal to amend and restate American Tower’s certificate of incorporation, which includes, among other things, an increase in the authorized number of American Tower Class A common stock from 500.0 million shares to 1.0 billion shares. American Tower currently has sufficient authorized shares of Class A common stock to consummate the merger. However, American Tower is obligated to issue up to approximately 186.5 million shares of Class A common stock in connection with the merger, including approximately 168.2 million shares issuable at the closing with respect to outstanding shares of SpectraSite common stock as of May 20, 2005 and up to approximately 18.3 million shares issuable pursuant to outstanding SpectraSite stock options and warrants as of May 20, 2005. Therefore, if the merger is consummated but the proposal to amend and restate the certificate of incorporation is not approved, American Tower would only have approximately 9.3 million authorized shares of Class A common stock that are

not already issued or reserved for issuance pursuant to outstanding options, warrants, convertible notes and its employee stock purchase plan as of May 20, 2005, which could limit American Tower’s flexibility to use capital stock for business and financial purposes in the future.

Resales of American Tower Class A common stock following the merger and additional obligations to issue American Tower Class A common stock may cause the market price of that stock to fall.

The merger will dilute the ownership position of the present stockholders of American Tower. As of May 20, 2005, American Tower had approximately 230.7 million shares of Class A common stock outstanding, approximately 30.0 million shares of Class A common stock subject to outstanding options and warrants, as well as outstanding convertible notes that, if converted, would represent approximately 39.4 million shares of Class A common stock and approximately 4.1 million shares of Class A common stock subject to its employee stock purchase plan. American Tower is obligated to issue approximately 186.5 million shares of Class A common stock in connection with the merger, including approximately 168.2 million shares issuable at the closing with respect to outstanding shares of SpectraSite common stock as of May 20, 2005 and up to approximately 18.3 million shares issuable pursuant to outstanding SpectraSite options and warrants as of May 20, 2005. The issuance of these new shares and the sale of additional shares of American Tower Class A common stock that may become eligible for sale in the public market from time to time upon exercise of options, including shares of American Tower Class A common stock subject to SpectraSite stock options assumed by American Tower in the merger, could have the effect of depressing the market price for American Tower Class A common stock.

American Tower’s foreign operations have added risks for SpectraSite stockholders.

SpectraSite stockholders that, after the merger, are stockholders of the combined company will be exposed to the risks posed by American Tower’s business operations in Mexico and Brazil, as well as any other possible foreign operations in the future, some of which are unique to those countries and not experienced in the United States. For example, American Tower’s business is subject to risks associated with doing business internationally, including changes in a specific country’s or region’s political or economic conditions, laws and regulations that restrict repatriation of earnings or other funds, difficulty in recruiting trained personnel, language and cultural differences and risks associated with changes in foreign currency exchange rates. American Tower has not historically engaged in significant hedging activities relating to its non-U.S. dollar operations.

Risks Associated with American Tower’s Business

For risks related to the operations of American Tower’s business, see the section captioned “Factors That May Affect Future Results” in American Tower’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2005 and incorporated by reference into this joint proxy statement/prospectus.

Because the risks and uncertainties facing each of American Tower and SpectraSite differ, the market price of the shares of American Tower Class A common stock after consummation of the merger and the results of operations, financial condition and liquidity of the combined entity may be affected by risks and uncertainties different from those that currently affect each of American Tower and SpectraSite separately.

Risks Associated with SpectraSite’s Business

For risks related to the operations of SpectraSite’s business, see the section captioned “Risk Factors” in SpectraSite’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2005 and incorporated by reference into this joint proxy statement/prospectus.

THE AMERICAN TOWER SPECIAL MEETING

Joint Proxy Statement/Prospectus

This joint proxy statement/prospectus is being furnished to you in connection with the solicitation of proxies by American Tower’s board of directors for the special meeting of American Tower stockholders.

This joint proxy statement/prospectus is first being furnished to American Tower stockholders on or about [·], 2005.

Date, Time and Place of the Special Meeting

The special meeting of American Tower stockholders will be held as follows:

[·], 2005

[·] a.m., local time

Palmer & Dodge LLP

111 Huntington Avenue

Boston, Massachusetts

Purpose of the Special Meeting

The purpose of the American Tower special meeting is:

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To act upon such other matters as may properly come before the meeting or any adjournments or postponements thereof.

Stockholder Record Date for the Special Meeting

American Tower’s board of directors has fixed the close of business on [·], 2005 as the record date for determining which American Tower stockholders are entitled to notice of and to vote at the American Tower special meeting or any adjournments or postponements of the American Tower special meeting. On the record date, there were [·] shares of American Tower Class A common stock outstanding, held by approximately [·] holders of record.

During the ten-day period before the special meeting, American Tower will keep a list of stockholders entitled to vote at the special meeting available for inspection during normal business hours at its offices in

Boston, Massachusetts, for any purpose germane to the special meeting. The list of stockholders will also be provided and kept at the location of the special meeting for the duration of the special meeting, and may be inspected by any stockholder who is present.

Quorum; Vote Required for Each Proposal

A majority of the outstanding shares of American Tower Class A common stock must be represented either in person or by proxy, to constitute a quorum at the American Tower special meeting. Proxies marked as abstentions and broker non-votes will be used in determining the number of shares present at the meeting. At the American Tower special meeting, each share of American Tower Class A common stock is entitled to one vote on all matters properly submitted to the American Tower stockholders.

Proposal Number One: The affirmative vote of the holders of a majority of shares of American Tower Class A common stock voting on Proposal Number One is required to approve the American Tower merger proposal, provided that the total votes cast represents over 50% in interest of all shares of American Tower Class A common stock entitled to vote.

Proposal Number Two: The affirmative vote of the holders of at least 66²/3% of the shares of American Tower Class A common stock outstanding as of the record date is required to approve the proposal to amend and restate American Tower’s Restated Certificate of Incorporation as more fully described in this joint proxy statement/prospectus.

The American Tower merger proposal is not conditioned on the proposal to amend and restate American Tower’s certificate of incorporation; however, the proposal to amend and restate the certificate of incorporation is conditioned on the consummation of the merger. Although American Tower currently has sufficient authorized shares of Class A common stock to consummate the merger, American Tower is seeking to amend and restate its certificate of incorporation to, among other things, increase the number of authorized shares. American Tower is obligated to issue up to approximately 186.5 million shares of Class A common stock in the merger, including approximately 168.2 million shares issuable at the closing with respect to outstanding shares of SpectraSite common stock as of May 20, 2005 and up to approximately 18.3 million shares issuable pursuant to outstanding SpectraSite options and warrants as of May 20, 2005. As a result of these obligations to issue shares of Class A common stock in the merger, if the merger is consummated, American Tower would only have approximately 9.3 million authorized shares of Class A common stock that are not already issued or reserved for issuance pursuant to outstanding options, warrants and convertible notes as of May 20, 2005. The American Tower board of directors believes that it is advisable and in the best interests of the stockholders to have available additional authorized but unissued shares in an amount adequate to provide for future needs. Although American Tower currently has no specific plans to issue the additional shares that would be authorized by this proposal, other than possible future issuances pursuant to existing share reservations, these shares will provide additional flexibility to use capital stock for business and financial purposes in the future. If the amended and restated certificate of incorporation is approved but the American Tower merger proposal is not approved or the merger is not consummated for any other reason, American Tower will not amend and restate its certificate of incorporation as set forth in this joint proxy statement/prospectus.

Proposal Number Three: The affirmative vote of the holders of a majority of the shares of American Tower Class A common stock voting on the proposal is required to permit American Tower’s board of directors or its chairman, in their discretion, to adjourn or postpone the special meeting if necessary to solicit further proxies.

The directors and executive officers of American Tower beneficially owned and were entitled to vote approximately [·]% of the outstanding shares of American Tower Class A common stock as of the record date, and each of them has indicated their intention to vote “FOR” each of the proposals.

The American Tower board of directors unanimously recommends that the American Tower stockholders vote “FOR” each of the proposals.

Adjournment or Postponement

If Proposal Number Three is approved at the special meeting, American Tower may adjourn or postpone the special meeting if necessary to solicit further proxies. Such adjournment or postponement may be with respect to (1) both Proposal Number One and Proposal Number Two, (2) Proposal Number One only or (3) Proposal Number Two only, in each case, to solicit additional proxies for the applicable proposal. In addition, American Tower may adjourn or postpone the special meeting as set forth in American Tower’s certificate of incorporation or by-laws or as otherwise permitted by law.

Proxies

American Tower stockholders may vote by returning the enclosed proxy card by mail, submitting an electronic proxy over the Internet, by telephone, or in person at the special meeting. All shares of American Tower Class A common stock represented by properly executed proxy cards received before or at the American Tower special meeting and all proxies properly submitted over the Internet or by telephone will, unless the proxies are revoked, be voted in accordance with the instructions indicated on those proxy cards or Internet or telephone submissions. If no instructions are indicated on a properly executed proxy card, the shares will be voted “FOR” each of the proposals. You are urged to indicate how to vote your shares, whether you vote by proxy card, over the Internet or by telephone.

If a properly executed proxy card is returned or properly submitted over the Internet or by telephone and the stockholder has abstained from voting on one or more of the proposals, the American Tower Class A common stock represented by the proxy will be considered present at the special meeting for purposes of determining a quorum, but will not be considered to have been voted on the abstained proposals.

If your shares are held in an account at a brokerage firm or bank, you must instruct them on how to vote your shares. If an executed proxy card is returned by a broker or bank holding shares that indicates that the broker or bank does not have discretionary authority to vote on the proposals, the shares will be considered present at the meeting for purposes of determining the presence of a quorum, but will not be considered to have been voted on the proposals. Your broker or bank will vote your shares only if you provide instructions on how to vote by following the information provided to you by your broker.

Abstentions, failures to vote and broker non-votes at the special meeting will have no effect on the American Tower merger proposal or the proposal to grant discretionary authority to American Tower’s board of directors or its chairman to adjourn the special meeting to further solicit proxies. Abstentions, failures to vote and broker non-votes for the proposal to amend and restate the American Tower certificate of incorporation will have the same effect as a vote against that proposal.

You can change your vote at any time before your proxy is voted at the special meeting. To revoke your proxy, you must either (1) notify the secretary of American Tower in writing, (2) mail a new proxy card dated after the date of the proxy you wish to revoke, (3) submit a later dated proxy over the Internet or by telephone by following the instructions on your proxy card or (4) attend the special meeting and vote your shares in person. Merely attending the special meeting will not constitute revocation of your proxy. If your shares are held in an account at a brokerage firm or bank, you should contact your brokerage firm or bank to change your vote.

American Tower is not aware of any business to be acted on at the American Tower special meeting, except as described in this joint proxy statement/prospectus. If any other matters are properly presented at the American Tower special meeting, or any adjournment or postponement of the special meeting, the persons appointed as proxies or their substitutes will have discretion to vote or act on the matter according to their best judgment and applicable law unless the proxy indicates otherwise.

Solicitation of Proxies

American Tower and SpectraSite will each pay one-half of the expenses incurred in connection with the printing and mailing of this joint proxy statement/prospectus. American Tower will also request banks, brokers and other intermediaries holding shares of American Tower Class A common stock beneficially owned by others to send this joint proxy statement/prospectus to, and obtain proxies from, the beneficial owners and will, upon request, reimburse the holders for their reasonable expenses in so doing. Solicitation of proxies by mail may be supplemented by telephone, telegram and other electronic means, advertisements and personal solicitation by the directors, officers or employees of American Tower. No additional compensation will be paid to directors, officers or employees for those solicitation efforts.

American Tower may engage one or more proxy solicitation firms to assist in obtaining proxies from its stockholders on a timely basis. As of the date of this joint proxy statement/prospectus, American Tower has not engaged a proxy solicitation firm or committed itself to the payment of any fees for this service.

THE SPECTRASITE SPECIAL MEETING

Joint Proxy Statement/Prospectus

This joint proxy statement/prospectus is being furnished to you in connection with the solicitation of proxies by SpectraSite’s board of directors for the special meeting of SpectraSite stockholders.

This joint proxy statement/prospectus is first being furnished to SpectraSite stockholders on or about [·], 2005.

Date, Time and Place of the Special Meeting

The special meeting of SpectraSite stockholders will be held as follows:

[·], 2005

[·] a.m., local time

SpectraSite, Inc.

400 Regency Forest Drive

Cary, North Carolina

Purpose of the Special Meeting

The purpose of the SpectraSite special meeting is:

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Stockholder Record Date for the Special Meeting

SpectraSite’s board of directors has fixed the close of business on [·], 2005 as the record date for determining which SpectraSite stockholders are entitled to notice of and to vote at the SpectraSite special meeting or any adjournment or postponement of the SpectraSite special meeting. On the record date, there were [·] shares of SpectraSite common stock outstanding, held by approximately [·] holders of record.

During the ten-day period before the special meeting, SpectraSite will keep a list of stockholders entitled to vote at the special meeting available for inspection during normal business hours at its offices in Cary, North Carolina, for any purpose germane to the special meeting. The list of stockholders will also be provided and kept at the location of the special meeting for the duration of the special meeting, and may be inspected by any stockholder who is present.

Quorum; Vote Required for Each Proposal

A majority of the outstanding shares of SpectraSite common stock must be represented, either in person or by proxy, to constitute a quorum at the SpectraSite special meeting. Proxies marked as abstentions and broker non-votes will be used in determining the number of shares present at the meeting. At the SpectraSite special meeting, each share of SpectraSite common stock is entitled to one vote on all matters properly submitted to the SpectraSite stockholders.

Proposal Number One: The affirmative vote of the holders of a majority of the shares of SpectraSite common stock outstanding as of the record date is required to approve the SpectraSite merger proposal.

Proposal Number Two: The affirmative vote of the holders of a majority of the shares of SpectraSite common stock voting on the proposal is required to permit SpectraSite’s board of directors or its chairman, in their discretion, to adjourn or postpone the special meeting if necessary to solicit further proxies in favor of the SpectraSite merger proposal.

The directors and executive officers of SpectraSite beneficially owned and were entitled to vote approximately [·]% of the outstanding shares of SpectraSite common stock as of the record date, and each of them has indicated their intention to vote “FOR” each of the proposals.

The SpectraSite board of directors unanimously recommends that the SpectraSite stockholders vote “FOR” each of the proposals.

Adjournment or Postponement

If Proposal Number Two is approved at the special meeting, SpectraSite may adjourn or postpone the special meeting if necessary to solicit further proxies for Proposal Number One. In addition, SpectraSite may adjourn or postpone the special meeting as set forth in SpectraSite’s certificate of incorporation or by-laws or as otherwise permitted by law.

Proxies

SpectraSite stockholders may vote by returning the enclosed proxy card by mail, submitting an electronic proxy over the Internet, by telephone, or in person at the special meeting. All shares of SpectraSite common stock represented by properly executed proxy cards received before or at the SpectraSite special meeting and all proxies properly submitted over the Internet or by telephone will, unless revoked, be voted in accordance with the instructions indicated on those proxy cards or Internet or telephone submissions. If no instructions are indicated on a properly executed proxy, the shares will be voted “FOR” each of the proposals. You are urged to indicate how to vote your shares, whether you vote by proxy card, over the Internet or by telephone.

If a properly executed proxy card is returned or properly submitted over the Internet or by telephone and the stockholder has abstained from voting on one or more of the proposals, the SpectraSite common stock represented by the proxy will be considered present at the special meeting for purposes of determining a quorum, but will not be considered to have been voted on the abstained proposals.

Abstentions, failures to vote and broker non-votes for the SpectraSite merger proposal will have the same effect as a vote against the SpectraSite merger proposal at the SpectraSite special meeting but will have no effect on the proposal to grant discretionary authority to SpectraSite’s board of directors or its chairman to adjourn the special meeting to further solicit proxies in favor of the SpectraSite merger proposal.

You can change your vote at any time before your proxy is voted at the special meeting. To revoke your proxy, you must either (1) notify the secretary of SpectraSite in writing, (2) mail a new proxy card dated after the date of the proxy you wish to revoke, (3) submit a later dated proxy over the Internet or by telephone by following the instructions on your proxy card or (4) attend the special meeting and vote your shares in person.

Merely attending the special meeting will not constitute revocation of your proxy. If your shares are held in an account at a brokerage firm or bank, you should contact your brokerage firm or bank to change your vote.

SpectraSite is not aware of any business to be acted on at the SpectraSite special meeting, except as described in this joint proxy statement/prospectus. If any other matters are properly presented at the SpectraSite special meeting, or any adjournment or postponement of the special meeting, the persons appointed as proxies or their substitutes will have discretion to vote or act on the matter according to their best judgment and applicable law unless the proxy indicates otherwise.

Appraisal Rights

Under Delaware law, SpectraSite’s stockholders are not entitled to appraisal rights in connection with the merger.

Solicitation of Proxies

American Tower and SpectraSite will each pay one-half of the expenses incurred in connection with the printing and mailing of this joint proxy statement/prospectus. SpectraSite will also request banks, brokers and other intermediaries holding shares of SpectraSite common stock beneficially owned by others to send this joint proxy statement/prospectus to, and obtain proxies from, the beneficial owners and will, upon request, reimburse the holders for their reasonable expenses in so doing. Solicitation of proxies by mail may be supplemented by telephone, telegram and other electronic means, advertisements and personal solicitation by the directors, officers or employees of SpectraSite. No additional compensation will be paid to directors, officers or employees for those solicitation efforts.

SpectraSite may engage one or more proxy solicitation firms to assist in obtaining proxies from its stockholders on a timely basis. As of the date of this joint proxy statement/prospectus, SpectraSite has not engaged a proxy solicitation firm or committed itself to the payment of any fees for this service.

You should not send in any stock certificates with your proxy card. If you are a SpectraSite stockholder, a transmittal letter with instructions for the surrender of your SpectraSite stock certificates will be mailed to you as soon as practicable after consummation of the merger.

PROPOSAL NUMBER ONE: THE MERGER PROPOSALS

This section describes certain aspects of the merger. While American Tower and SpectraSite believe this description covers the material terms of the merger, this summary may not contain all of the information that is important to you. You should read this entire joint proxy statement/prospectus, including the annexes, carefully for a more complete understanding of the merger and the terms of the merger agreement.

General Description of the Merger

At the effective time, SpectraSite will be merged with and into Asteroid Merger Sub, LLC, a Delaware limited liability company and a wholly owned subsidiary of American Tower formed solely for the purpose of engaging in the merger. Asteroid Merger Sub will be the surviving entity and will continue as a wholly owned subsidiary of American Tower. As a result of the merger, each share of SpectraSite common stock outstanding at the effective time will be converted automatically into the right to receive 3.575 shares of American Tower Class A common stock, with cash paid for any fractional share.

However, at the option of American Tower, the structure of the merger may be changed to consist of a merger of Asteroid Merger Sub with and into SpectraSite in which case SpectraSite will survive and continue as a direct wholly owned subsidiary of American Tower, subject to certain other agreements and conditions, including the receipt by each of American Tower and SpectraSite from its respective legal counsel on the closing date of the merger of an opinion stating that the merger will be treated for U.S. federal income tax purposes as a “reorganization” within the meaning of Section 368(a) of the Internal Revenue Code and that American Tower and SpectraSite will each be a party to that reorganization within the meaning of Section 368(b) of the Internal Revenue Code. See the section captioned “THE MERGER AGREEMENT—Form of Merger” beginning on page 73 for a complete discussion of the circumstances under which the surviving entity can be changed pursuant to the merger agreement.

Based on the number of shares of SpectraSite common stock and American Tower Class A common stock outstanding as of May 20, 2005 and the exchange ratio, approximately 168.2 million shares of American Tower Class A common stock will be issuable to SpectraSite stockholders pursuant to the merger agreement, representing approximately 42% of the American Tower Class A common stock outstanding immediately after the merger. Based on shares of SpectraSite common stock issuable pursuant to outstanding stock options or warrants as of May 20, 2005 and the exchange ratio, options or warrants to purchase approximately 18.3 million additional shares of American Tower Class A common stock will be assumed by American Tower in the merger. This assumes that none of SpectraSite’s stock options or warrants are exercised between May 20, 2005 and the effective time. Although American Tower is seeking to amend and restate its certificate of incorporation to, among other things, increase the number of authorized shares of Class A common stock, American Tower currently has sufficient authorized shares of Class A common stock to consummate the merger and to reserve sufficient shares for issuance upon the exercise of SpectraSite’s outstanding stock options and warrants.

Background of the Merger

In the first quarter of 2003, American Tower’s management publicly stated that it would continue to be interested in participating in the consolidation of the wireless communications tower industry on terms that are consistent with the perceived benefits listed below and that create long-term value for American Tower stockholders. Particularly, in American Tower’s 2002 Annual Report to Stockholders, management stated that a key element of its strategy was participation in tower industry consolidation. American Tower management stated its belief that a compelling rationale for consolidation among tower companies existed because:

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a more extensive network would better position a tower company to provide more comprehensive service to customers and to support the infrastructure requirements of future generations of wireless communication technologies;

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combining with one or more other tower companies should result in improvements in cost structure efficiencies, with a corresponding positive impact on operating results; and

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these benefits should, in turn, enhance access to capital and accelerate the de-levering process.

As participants in the wireless communications tower industry, the senior management teams of each of American Tower and SpectraSite are generally familiar with each other’s business, and have met and meet from time to time at industry conferences and similar events. On an ongoing basis, the boards of directors and managements of each of American Tower and SpectraSite independently evaluate options for achieving its long-term strategic goals and enhancing stockholder value.

In November 2003, Steven Dodge, the then-current Chairman of the Board of American Tower, and James Taiclet, the President and Chief Executive Officer of American Tower, met with Stephen Clark, the Chairman of the Board, President and Chief Executive Officer of SpectraSite, to discuss the wireless telecommunications tower industry in general and to explore whether there was mutual potential interest in exploring a business combination between American Tower and SpectraSite. Shortly thereafter, Mr. Clark and David Tomick, the then-current Chief Financial Officer of SpectraSite, met with Mr. Taiclet and Brad Singer, the Chief Financial Officer of American Tower, to further explore whether there was mutual potential interest in a business combination between American Tower and SpectraSite. As a follow-up to these meetings, representatives of American Tower contacted a representative of the largest SpectraSite stockholder, who was also a member of the board of directors of SpectraSite, and these individuals also discussed whether there was mutual potential interest in a business combination.

The discussions between American Tower and SpectraSite in November 2003 terminated at an early stage due to differences regarding their respective strategies and the possible terms of a transaction, and at no time did the discussions progress beyond initial exchanges of views on long-term strategy and the terms of a possible business combination.

In February 2004, Mr. Dodge retired from American Tower’s board of directors, and Mr. Taiclet was elected Chairman of the Board of American Tower.

On July 13, 2004, Messrs. Taiclet and Clark met to discuss American Tower’s and SpectraSite’s respective views on consolidation of the wireless communications tower industry and American Tower’s interest in a possible business combination with SpectraSite. Mr. Clark indicated that SpectraSite was carefully considering long-term strategic options. Nothing further developed and at no time did the discussions in July 2004 progress beyond initial exchanges of views on consolidation in the wireless communications tower industry and long-term strategy.

On October 7, 2004, Mr. Singer met Timothy Biltz, Chief Operating Officer of SpectraSite, following a meeting of the board of directors of FiberTower Corporation, of which they both are members. During this meeting, Mr. Biltz reiterated that SpectraSite was carefully considering long-term strategic options and noted that it was SpectraSite’s belief that wireless carrier consolidation would be a significant catalyst for tower company consolidation.

In November 2004, SpectraSite’s board of directors formed a Corporate Strategy Committee. The primary objectives of the Corporate Strategy Committee are to assist the SpectraSite board of directors by (1) identifying strategic opportunities for SpectraSite, (2) identifying strategic risks facing SpectraSite, (3) overseeing and advising SpectraSite’s senior management in the development of a strategic plan to maximize long-term stockholder value and (4) assisting SpectraSite’s senior management in determining the resources necessary for, and the effectiveness of, the strategic plan.

On December 10, 2004, the Corporate Strategy Committee engaged a nationally recognized consulting firm to assist the committee in its efforts to further develop a strategy to maximize long-term stockholder value.

The Corporate Strategy Committee, with the assistance of SpectraSite’s management, outside consultant, legal counsel and financial advisors, explored and reviewed long-term strategic alternatives in the best interests of SpectraSite’s stockholders. During the period from November 2004, when it was formed, through May 2005, when the merger agreement was finalized, the Corporate Strategy Committee met seven times and received five presentations from the consulting firm as well as a presentation from a nationally recognized investment banking firm. These presentations covered a range of related topics, including (1) factors that influence SpectraSite’s strategic opportunities, such as wireless carrier consolidation, actions of tower company competitors and drivers for new demand for tower space, (2) strategic opportunities and (3) adjacent opportunities. In performing its mandate, the Corporate Strategy Committee (1) considered the business, operations, financial condition, cash flow and prospects of SpectraSite continuing on a standalone basis while exploring the potential to reinvest its cash flow in its core business or to enter into new ancillary businesses, (2) analyzed possible recapitalization alternatives, including increasing leverage in order to more aggressively repurchase SpectraSite common stock or pay dividends to common stockholders and (3) actively explored and evaluated the possibility of business combinations with potential strategic and financial partners, including management discussions of potential transactions with likely strategic partners.

On December 17, 2004, Mr. Clark initiated a telephone conversation with Mr. Taiclet. During this conversation, Mr. Clark indicated that in connection with its on-going strategic analysis, SpectraSite was interested in discussing a possible business combination with American Tower. Messrs. Taiclet and Clark agreed that each company would separately evaluate whether it was interested in pursuing a business combination and decided to have a further conversation in the near future after each company had completed its evaluation.

On January 3, 2005, Messrs. Taiclet and Clark had a telephone conversation to further discuss a potential business combination of American Tower and SpectraSite and, during this conversation, determined to meet in person at an upcoming media and telecommunications conference in Phoenix, Arizona to continue these discussions.

On January 5, 2005, Mr. Biltz called Mr. Singer to discuss the upcoming meeting between Messrs. Taiclet and Clark. Mr. Biltz indicated that the announcement on December 15, 2004 by Sprint Corporation and Nextel Communications, Inc. that they had entered into a definitive merger agreement would likely intensify the focus on consolidation in the tower industry.

On January 10, 2005, upon the recommendation of SpectraSite’s Corporate Strategy Committee, SpectraSite’s board of directors received a detailed presentation from a nationally recognized investment banking firm regarding strategic opportunities. The presentation included (1) an overview of wireless carrier consolidation, (2) a review of the impact of wireless carrier consolidation on the tower landscape, (3) an evaluation of SpectraSite’s strategic alternatives, including potential business combinations with American Tower and other potential parties, (4) an analysis of significant shareholder overlap among selected tower companies and (5) a summary of potential buyers of tower assets. Following the presentation, SpectraSite’s board of directors then held a discussion about the relative benefits and risks of a possible business combination transaction with certain tower companies, including American Tower. At this meeting, SpectraSite’s board of directors authorized SpectraSite’s management to continue to explore potential business combinations, including with American Tower.

During the period from January 2005 through March 2005, in addition to the discussion with American Tower, SpectraSite had periodic, preliminary discussions with representatives of two other publicly traded tower companies. These discussions terminated at an early stage and at no time did the discussions progress beyond initial exchanges of views on consolidation in the wireless communications industry, long-term strategy and the terms of a possible business combination.

On January 12, 2005, Messrs. Taiclet and Clark met in Phoenix, Arizona and further discussed a business combination between the companies. At this meeting, Mr. Taiclet indicated that he would further evaluate a

business combination with SpectraSite and would discuss the possibility of a business combination with American Tower’s board of directors.

On January 26, 2005, SpectraSite’s board of directors met to discuss strategic alternatives. At this meeting, Paul, Weiss, Rifkind, Wharton & Garrison LLP, its legal counsel, gave a presentation regarding the legal and fiduciary duties related to considering possible strategic opportunities. The SpectraSite board of directors also received a detailed presentation from its outside consultant regarding strategic alternatives, including the factors that influence SpectraSite’s strategic opportunities, such as wireless carrier consolidation, actions of tower company competitors and drivers for new demand. At the same meeting, Lehman Brothers Inc. and Evercore Partners, SpectraSite’s financial advisors, gave a preliminary presentation regarding a review of strategic alternatives, including (1) a review of the likely impact on tower companies of wireless carrier consolidation, (2) the current state of the tower industry, (3) the benefits and considerations of a number of strategic alternatives, including potential business combinations with American Tower and certain other tower companies and (4) key considerations in a strategic transaction, such as valuation, ownership, capital structure, certainty of closing, governance and social issues. Following the presentation, SpectraSite’s board of directors held a discussion about strategic aspects and the relative benefits and risks of a possible business combination transaction with certain tower companies, including American Tower. At this meeting, SpectraSite’s board of directors authorized SpectraSite’s management to continue to explore potential business combinations, including with American Tower, and to continue to refine the analysis contained in the preliminary presentation.

On February 24, 2005, SpectraSite’s board of directors met. SpectraSite’s senior management updated the board of directors with respect to potential mergers and acquisitions activity. In addition, the chairman of the Corporate Strategy Committee presented a report on the status of the consultant’s analysis and the committee’s efforts regarding the development of a strategy to create and maximize long-term stockholder value.

During February and March 2005, in preparation for an upcoming meeting of American Tower’s board of directors, Messrs. Taiclet and Singer, with representatives of Citigroup Global Markets Inc., American Tower’s financial advisor, prepared a preliminary comparative analysis of certain business combination transactions with a number of companies in the tower industry, including the financial and strategic aspects of a possible business combination with SpectraSite. On March 17, 2005, American Tower’s board of directors considered a preliminary presentation by Citigroup that summarized this analysis. Following the presentation by Citigroup, American Tower’s board of directors then held a discussion about the relative benefits and risks of a possible business combination transaction with a number of tower companies, including SpectraSite. This discussion included the consideration of indicative exchange ratios that might be offered in such a transaction with various companies and the expected effects of such a transaction on the business and financial position of American Tower as well as a discussion of the likely success of a business combination proposal by American Tower to these other companies. At this meeting, American Tower’s board of directors authorized American Tower’s management to continue to evaluate a potential business combination with SpectraSite and to continue to refine the analysis contained in the preliminary presentation.

On March 21, 2005, Messrs. Taiclet and Singer initiated telephone conversations with Messrs. Clark and Biltz to discuss organizing a meeting between Messrs. Taiclet and Clark to explore whether the parties had any mutual interest in moving forward with more formal discussions regarding a possible business combination between the two companies. On March 28, 2005, Messrs. Singer and Biltz met and discussed generally the possible business combination between the two companies.

On April 4, 2005, Messrs. Taiclet and Clark met in New York, New York. During this meeting, Messrs. Taiclet and Clark discussed the potential strategic fit of the two organizations and the complementary nature of their tower portfolios in greater detail, as well as the potential synergies that might be derived from a business combination. In addition, Messrs. Taiclet and Clark discussed the process by which the companies would further evaluate a business combination. Messrs. Taiclet and Clark believed that the relative stock prices of American Tower and SpectraSite, changes in industry dynamics, ongoing consolidation of wireless carriers, and views concerning the management, long-term strategy and direction of the combined company rendered the companies

a better potential strategic fit at this time as compared to when the companies previously held preliminary discussions. At this meeting, Mr. Clark also provided a preliminary indication, based upon certain assumptions and subject to further due diligence by both parties and agreement as to final terms, that SpectraSite would be willing to consider in a potential business combination with American Tower that included an exchange ratio range between 3.70 and 3.75 shares of American Tower Class A common stock for each share of SpectraSite common stock.

During the week of April 4, 2005, and in conjunction with the initial discussions between Messrs. Taiclet and Clark, the companies continued consulting with their respective financial and legal advisors regarding a possible business combination. Each company, working with its financial and legal advisors, conducted due diligence investigations using publicly available materials and analyzed a possible business combination. These consultations continued throughout the remaining merger discussions.

On April 5, 2005, Mr. Taiclet initiated a telephone conversation with Mr. Clark to convey American Tower’s position in respect of an acceptable exchange ratio range between 3.55 and 3.65 for a business combination with SpectraSite.

On April 6, 2005, Messrs. Taiclet and Singer met with Messrs. Clark and Biltz in Boston, Massachusetts to further discuss the possibility of a business combination between the two companies and to establish a process and timeline for pursuing a transaction. At this meeting, the parties discussed entering into customary confidentiality and exclusivity arrangements and discussed the process by which the due diligence investigation by the parties would occur. Also, the parties discussed possible approaches for agreeing upon valuation in a transaction based upon the enterprise values of American Tower and SpectraSite taking into account expected cost synergies and transaction costs. While the parties also further discussed the two companies’ positions regarding a possible exchange ratio for the transaction, neither party modified its position as to an acceptable exchange ratio.

On April 7, 2005, American Tower’s board of directors met to discuss the possible business combination with SpectraSite as well as the initial conversations between SpectraSite management and American Tower management. At this meeting, Mr. Taiclet apprised American Tower’s board of directors of his and Mr. Singer’s meeting with Messrs. Clark and Biltz, as well as the approach to valuation. Also, representatives from Citigroup presented a preliminary analysis with respect to its valuation of SpectraSite. After discussion, American Tower’s board of directors authorized senior management to further explore the possibility of a business combination transaction with SpectraSite. Thereafter, in addition to the formal board meetings described below, Mr. Taiclet continued from time to time to update members of American Tower’s board of directors on the status of the discussions until the signing of the merger agreement.

After American Tower’s board of directors meeting on April 7, 2005, Mr. Taiclet communicated by e-mail to Mr. Clark to confirm American Tower’s interest in continuing further discussions regarding the possibility of exploring a business combination between the two companies.

On April 11, 2005, SpectraSite’s board of directors met to discuss a possible business combination with American Tower as well as the initial conversations between American Tower management and SpectraSite management. At this meeting, Mr. Clark apprised SpectraSite’s board of directors of his and Mr. Biltz’s meetings and telephone conversations with Messrs. Taiclet and Singer, including the approach to valuation, management, board composition, long-term strategy and other matters that were discussed. Also at this meeting, Paul, Weiss advised the SpectraSite board of directors concerning its legal and fiduciary duties in connection with SpectraSite’s exploration of strategic alternatives and possible entry into exclusive negotiations with American Tower. In addition, Lehman Brothers and Evercore gave a detailed presentation regarding strategic alternatives, including (1) an overview of certain discussions between SpectraSite senior management and certain potential strategic partners, (2) an overview of the potential terms of the proposed business combination with American Tower, such as the structure and proposed composition of the board of directors and management of the

combined company, and of the estimated synergies in such a transaction and key financial characteristics of the combined company and (3) the likelihood of, and rationale for, consolidation in the tower industry. After discussion, SpectraSite’s board of directors authorized senior management to continue to explore the possibility of a business combination transaction with American Tower. Thereafter, in addition to the formal board meetings described below, Mr. Clark continued from time to time to update members of SpectraSite’s board of directors on the status of the discussions until the signing of the merger agreement.

On April 11, 2005, Mr. Clark initiated a telephone conversation with Mr. Taiclet to confirm SpectraSite’s interest in continuing further discussions regarding a business combination between the two parties. On April 11, 2005, American Tower and SpectraSite executed a confidentiality agreement and an agreement that provided for mutually exclusive negotiations through May 3, 2005.

During the week of April 11, 2005, SpectraSite’s senior management, along with Lehman Brothers, Evercore and Paul, Weiss, continued to assess the financial, legal and strategic aspects of a possible business combination transaction with American Tower. Similarly, during the week of April 11, 2005, American Tower’s senior management, Citigroup, and its legal counsel, King & Spalding LLP, continued to assess the financial, legal and strategic aspects of a possible business combination transaction with SpectraSite. During this time, representatives of American Tower and SpectraSite and their respective legal and financial advisors exchanged due diligence information and arranged multiple conference calls to discuss the proposed timetable for a business combination, preparation of data rooms for each company and the overall due diligence process.

On April 13, 2005, Messrs. Taiclet and Biltz met in Cary, North Carolina, to discuss in greater detail the key business aspects and relationships of American Tower and SpectraSite, as well as certain governance, management and employee considerations involved with a possible business combination. On April 14, 2005, Mr. Taiclet met with Mr. Clark again to discuss the companies’ respective businesses, as well as certain governance, management and employee matters.

On April 19, 2005, Mr. Singer, and Hal Hess, Executive Vice President and General Counsel of American Tower, met with Mr. Biltz and Mark Slaven, Chief Financial Officer of SpectraSite, and their respective legal and financial advisors, as well as other management employees of the two companies, in New York, New York. During this meeting, each of the parties gave presentations regarding its business and financial condition and engaged in extended discussions regarding a wide variety of matters that had arisen during the course of the due diligence investigation being undertaken by each party together with its advisors. These discussions included a discussion of the potential cost synergies of a merger, governance of the combined company, various matters regarding key customer relationships and the proposed structure for a potential business combination. Although the parties did not reach agreement on these issues, a proposed plan for moving forward with exploring a possible transaction also was discussed in principle during this meeting.

On April 19, 2005, King & Spalding, distributed an initial draft merger agreement to SpectraSite and its representatives.

On April 20, 2005, SpectraSite’s board of directors met to review developments in the on-going discussions with American Tower. Paul, Weiss advised the SpectraSite board of directors concerning the fiduciary duties applicable in connection with SpectraSite’s exploration of a business combination with American Tower. In addition, Lehman Brothers and Evercore made a detailed presentation regarding the proposed strategic transaction with American Tower, including (1) an update on the process and timing of the proposed transaction, (2) an update on due diligence and discussions between SpectraSite, American Tower and their respective advisors, (3) management’s estimated cost synergies and (4) potential exchange ratios.

During the week of April 18, 2005, SpectraSite’s senior management, along with Lehman Brothers, Evercore and Paul, Weiss, continued to assess the financial, legal and strategic aspects of a possible business

combination transaction with American Tower. Similarly, during the week of April 18, 2005, American Tower’s senior management, along with Citigroup and King & Spalding, continued to assess the financial, legal and strategic aspects of a possible business combination transaction with SpectraSite. During this time, representatives of American Tower and SpectraSite and their respective legal and financial advisors continued to exchange and refine due diligence information, and continued to conduct conference calls to discuss the business combination and refine the issues with respect to valuation and the terms of the merger agreement.

Also during the week of April 18, 2005, SpectraSite’s senior management and Paul, Weiss prepared comments and proposed revisions to the draft merger agreement. These comments and revisions were distributed by Paul, Weiss to American Tower and its representatives on April 22, 2005.

On April 25, 2005, Messrs. Taiclet and Clark had a telephone conversation during which they discussed the status of each company’s respective due diligence efforts, as well as the timeframe and process for a potential business combination.

On April 26, 2005, Mr. Taiclet met with Mr. Clark, Patricia Higgins, SpectraSite’s lead independent director, and Dean Douglas, a member of SpectraSite’s board of directors. At this meeting, the parties discussed the long-term strategy of American Tower for the combined company, the benefits of the merger and governance issues related to the board of directors of the potential combined company. After this meeting, Messrs. Taiclet and Clark held a separate meeting to discuss various due diligence matters and the effect that those matters had on valuation.

On April 26, 2005, Citigroup, Lehman Brothers and Evercore conducted phone conversations to discuss the possible exchange ratio for the merger. Also on April 26, 2005, King & Spalding and Paul, Weiss met in New York, New York to discuss the other issues in the draft merger agreement.

On April 27, 2005, American Tower’s board of directors met to discuss the status of the discussions regarding a possible business combination transaction and the results of the parties’ valuation analyses and due diligence investigations. At this meeting, American Tower’s board of directors considered the indicative exchange ratios suggested by the various valuation analyses performed by Citigroup and management, and authorized Mr. Taiclet to propose to Mr. Clark an exchange ratio of 3.55 shares of American Tower Class A common stock for each share of SpectraSite common stock and to continue to negotiate a possible transaction within a 3.55 to 3.65 exchange ratio range.

Following the board meeting on April 27, 2005, Mr. Taiclet indicated to Mr. Clark that based on American Tower’s most recent valuation analysis and its understanding of the current status of a number of SpectraSite’s key customer relationships, American Tower was willing to offer 3.55 shares of American Tower Class A common stock for each share of SpectraSite common stock. In response to American Tower’s position, Mr. Clark indicated that he did not believe the SpectraSite board of directors would be willing to proceed with a transaction at that exchange ratio.

On April 28, 2005, representatives of Evercore contacted representatives of Citigroup and indicated that SpectraSite would be interested in continuing merger discussions with American Tower if American Tower was willing to offer an exchange ratio that was greater than 3.55 shares of American Tower Class A common stock for each share of SpectraSite common stock. In response to SpectraSite’s indication of interest, American Tower’s management decided to continue to explore a business combination. As a result of these communications between Evercore and Citigroup, American Tower’s management and SpectraSite’s management and their respective financial and legal advisors continued to refine the financial and legal due diligence and continued their efforts to reach a definitive merger agreement.

In connection with the continuation of discussions between the parties’ legal advisors regarding the terms of a definitive merger agreement, SpectraSite identified a number of issues in the draft of the merger agreement that were still open and would need to be resolved in SpectraSite’s favor in order for SpectraSite to be willing to proceed with a business combination at the exchange ratios being discussed. In particular, Paul, Weiss stated SpectraSite’s position that the merger agreement should (1) require the parties to expend a higher level of “reasonable best efforts” to accommodate any conditions or required divestitures imposed by antitrust authorities in connection with the proposed combination, (2) contain restrictions on American Tower’s operations and financing activities more consistent with those imposed on SpectraSite in the current draft of the merger agreement, (3) not contain any condition related to consents or amendments to, or the refinancing of, SpectraSite’s credit facility or outstanding senior notes, (4) contain a satisfactory definition of the term Material Adverse Effect and (5) provide for a 90-day restriction on American Tower’s ability to terminate SpectraSite employees following the merger as well as certain other provisions regarding employee retention benefits designed to ensure a successful transition and to preserve SpectraSite’s employee base in the event that the merger is not completed.

On April 29, 2005, Messrs. Taiclet and Clark held a telephone meeting to discuss various terms of the merger agreement, including the key provisions that had been identified by Paul, Weiss.

Also on April 29, 2005, representatives of the parties’ financial advisors held a series of discussions aimed at determining a mutually acceptable exchange ratio near the middle of the 3.55 to 3.65 exchange ratio range discussed by Messrs. Taiclet and Clark on April 5, 2005.

From April 28, 2005 through May 3, 2005, negotiations on the merger agreement continued until the merger agreement was executed by the parties on May 3, 2005. During that time period, both parties and their respective representatives and advisors continued their legal, financial and accounting due diligence activities and negotiation of definitive documentation.

On May 2, 2005, SpectraSite’s board of directors met at its regularly scheduled meeting, which commenced following SpectraSite’s Annual Meeting of Stockholders held earlier the same day. Prior to the meeting, SpectraSite’s board of directors had been provided with materials relating to the proposed transaction, including a draft of the merger agreement and a presentation prepared by Lehman Brothers and Evercore. At this board of directors meeting, SpectraSite’s board of directors received a detailed presentation from its outside consultant on core growth options, ancillary growth opportunities and strategic alternatives. SpectraSite’s senior management reviewed the status of discussions with American Tower and the process to date in exploring the possibility of a business combination transaction with American Tower. SpectraSite’s senior management also reviewed the strategic benefits of the possible transaction, the results of the continued due diligence investigation of American Tower and the risks of the possible transaction. SpectraSite’s board of directors discussed with SpectraSite’s senior management, legal counsel and financial advisors its views concerning the potential benefits of and the risks associated with the possible business combination transaction. In addition, Lehman Brothers and Evercore made a presentation to SpectraSite’s board of directors analyzing the possible business combination of American Tower and SpectraSite. Representatives of Ernst & Young LLP, SpectraSite’s independent registered public accountants, then provided SpectraSite’s board of directors with an overview of its accounting due diligence efforts and representatives of Paul, Weiss provided the board of directors with an overview of the legal due diligence. Following these reports, Paul, Weiss reviewed in detail the terms and provisions of the draft merger agreement and the issues in the merger agreement that were still subject to negotiation. A discussion took place among the members of SpectraSite’s board of directors concerning the possible transaction, including discussion of the strategic benefits of the business combination, the risks of the transaction, the financial aspects of the transaction, the regulatory issues concerning the transaction and the anticipated synergies to be derived from the proposed business combination. At the conclusion of the meeting, SpectraSite’s board of directors authorized Mr. Clark and its advisors to continue to work to finalize the potential business combination transaction with American Tower.

On the evening of May 2, 2005, American Tower’s board of directors met to review the status of discussions with SpectraSite and the process to date in exploring the possibility of a business combination transaction with SpectraSite. Prior to the meeting, American Tower’s board of directors had been provided with materials relating to the proposed transaction, including a draft of the merger agreement and a summary of the key terms of the merger agreement and an updated presentation prepared by Citigroup that contained valuation analyses of American Tower and SpectraSite and the transaction, including the financial and strategic aspects of the proposed business combination with SpectraSite. At the meeting, American Tower’s board of directors reviewed with representatives of Citigroup the materials prepared by Citigroup further refining the analysis of a possible business combination of American Tower and SpectraSite and the related valuation matters related to SpectraSite. American Tower’s board of directors then discussed with senior management and American Tower’s financial and legal advisors the results of its continued due diligence investigation, as well as the updated status of certain of SpectraSite’s key customer relationships. At the conclusion of the meeting, American Tower’s board of directors authorized Mr. Taiclet to propose to SpectraSite an exchange ratio of 3.575 to 3.60 shares of American Tower Class A common stock for each share of SpectraSite common stock depending on the resolution of the remaining issues in the draft merger agreement.

After American Tower’s board of directors meeting, Mr. Taiclet initiated a telephone conversation with Mr. Clark to resolve the exchange ratio and final open issues. In their conversation, Messrs. Taiclet and Clark resolved the open issues and discussed bringing to their respective boards of directors a merger transaction between American Tower and SpectraSite with an exchange ratio of 3.575 shares of American Tower Class A common stock for each share of SpectraSite common stock. Following the conversation between Messrs. Taiclet and Clark on the evening of May 2, 2005 and continuing into the evening of May 3, 2005, the parties and their legal and financial advisors worked to finalize the remaining open due diligence items and to complete the definitive merger agreement as well as the related disclosure schedules.

At a meeting of American Tower’s board of directors held at 8:00 p.m. on May 3, 2005, American Tower’s board of directors met to consider the proposed business combination with SpectraSite. Prior to the meeting, American Tower’s board of directors had been provided with materials relating to the proposed transaction, including a draft of the merger agreement and a summary of the key terms of the merger agreement. During this meeting, American Tower’s internal legal counsel and King & Spalding summarized again for the American Tower board of directors previous advice provided regarding its legal duties and responsibilities in connection with the possible business combination transaction. In addition, King & Spalding reviewed the material terms and conditions of the merger agreement and the resolution of the remaining issues in the merger agreement. Senior management of American Tower then reviewed with American Tower’s board of directors the strategic benefits of the possible transaction, the results of the due diligence review of SpectraSite and the risks of the possible transaction, and Citigroup reviewed with American Tower’s board of directors financial aspects of the transaction and confirmed its financial analysis regarding the proposed business combination transaction. In addition, Citigroup rendered to American Tower’s board of directors an opinion as of the date of the meeting and based on the assumptions, qualifications and limitations contained therein, that the exchange ratio was fair, from a financial point of view, to American Tower. An extended discussion took place among the members of American Tower’s board of directors concerning the possible transaction, including discussion of the strategic benefits of the business combination, the risks of the transaction, the financial aspects of the transaction, the regulatory issues concerning the transaction and the anticipated cost synergies to be derived from the proposed business combination. Following a thorough discussion, American Tower’s board of directors unanimously voted to approve and adopt the merger and the merger agreement and to recommend to the American Tower stockholders that they approve the issuance of American Tower Class A common stock in connection with the merger, and authorized management to take certain other actions designed to accomplish various transactions contemplated under the merger agreement and associated documents.

At a meeting of SpectraSite’s board of directors held at 8:30 p.m. on May 3, 2005, SpectraSite’s board of directors met to consider the proposed business combination with American Tower. Prior to the meeting, SpectraSite’s board of directors had been provided with materials relating to the proposed transaction, including an update of the Lehman Brothers and Evercore presentation and a revised draft of the merger agreement. During

this meeting, Paul, Weiss summarized again for the SpectraSite board of directors previous advice provided regarding its legal duties and responsibilities in connection with the possible business combination transaction. In addition, Paul, Weiss reviewed the final terms and conditions of the merger agreement including the issues in the merger agreement that were resolved subsequent to the May 2, 2005 SpectraSite board of directors’ meeting. Lehman Brothers and Evercore reviewed financial aspects of the transaction and confirmed its financial analysis regarding the proposed business combination transaction. In addition, Lehman Brothers and Evercore each rendered to SpectraSite’s board of directors an opinion as of the date of the meeting and based on the assumptions, qualifications and limitations contained therein, that the exchange ratio of 3.575 shares of American Tower Class A common stock for each share of SpectraSite common stock was fair, from a financial point of view, to SpectraSite stockholders. Following a thorough discussion, SpectraSite’s board of directors unanimously voted to approve and adopt the merger and the merger agreement and to recommend to the SpectraSite stockholders that they approve and adopt the merger agreement, and authorized management to take certain other actions designed to accomplish various transactions contemplated under the merger agreement and associated documents.

After negotiation of the final terms of the merger agreement, representatives of American Tower and representatives of SpectraSite executed the merger agreement.

On the morning of May 4, 2005, American Tower and SpectraSite issued a joint press release announcing the proposed merger of American Tower and SpectraSite.

American Tower’s Reasons for the Merger

In reaching its conclusion to approve the merger, the American Tower board of directors consulted with American Tower’s management, as well as with its financial and legal advisors, and considered a variety of factors weighing in favor of the merger including, without limitation, the following:

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The enhanced position of the combined company in the wireless communications tower industry due to the increase in the size and quality of the combined company’s U.S. communications tower portfolio and the improved ability of the combined company to satisfy the needs of its wireless carrier customers. Specifically, it was anticipated that the merger would:

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increase American Tower’s U.S. tower base by combining America Tower’s approximately 12,000 towers with SpectraSite’s approximately 8,000 towers within the competitive wireless communications tower industry, resulting in the largest U.S. communications tower portfolio of approximately 20,000 towers;

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allow American Tower to combine its tower portfolio, which is less concentrated in large metropolitan areas, with SpectraSite’s portfolio, which has greater concentration in the 100 top basic trading area markets, to enable the combined company to address both the network capacity and coverage needs of wireless carrier customers;

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enhance American Tower’s relationships with its national wireless carrier customers by doubling the share of these carriers’ wireless networks from approximately 10% to almost 20%;

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increase the combined company’s flexibility to negotiate mutually beneficial arrangements with its key wireless carrier customers; and

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provide American Tower the benefits of SpectraSite’s “in-building” distributed antenna system business, which is a complementary product offering that enables wireless carriers to provide services to customers in large buildings such as shopping malls, hotels and casinos.

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The expectation that the combined company would be able to achieve improved operational performance compared to either of American Tower or SpectraSite on a standalone basis. In particular, the merger would:

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offer the combined company the opportunity to achieve significant cost synergies, which American Tower estimates could be up to approximately $30.0 to $35.0 million annually, primarily by

reducing the two companies’ expected aggregate standalone selling, general and administrative costs;

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allow the combined company to operate its U.S. tower portfolio more efficiently by combining the field management of its tower sites in certain markets; and

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allow the combined company the opportunity to draw the best talent from the employee and managerial pool of the combined company and to identify and apply best practices from both companies.

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The opportunity to improve expected risk adjusted returns to American Tower stockholders. Specifically, the combination of American Tower with SpectraSite would:

•

offer American Tower improved financial flexibility as a result of SpectraSite’s lower leverage level and the expected lower aggregate leverage level of the combined company;

•

accelerate American Tower’s ability to return cash to its stockholders;

•

afford American Tower the opportunity to lower its overall cost of capital as a result of the combined company’s lower overall leverage, improved financial flexibility and greater scale and diversification of asset base; and

•

broaden American Tower’s potential stockholder base by creating a combined company with a substantially larger equity market capitalization, and one of the largest focused on the U.S. wireless communications business, which may be attractive to a broader pool of potential investors.

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The financial performance and condition, business operations and prospects of each of American Tower, SpectraSite and the combined company.

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The strategic alignment of American Tower’s and SpectraSite’s focus on the tower leasing business, dedication to operational execution and improvement, and commitment to optimizing their respective capital structures.

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The then-current financial market conditions and historical market prices, volatility and trading information with respect to shares of American Tower Class A common stock and SpectraSite common stock.

•

The possible stock market reaction to the merger, and the expected impact of the announcement of the merger on the business operations and on the stockholders, creditors, customers and employees of each of American Tower and SpectraSite.

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The financial presentation and opinion of Citigroup Global Markets Inc., American Tower’s financial advisor, dated May 3, 2005, to the effect that, as of that date and based on and subject to the matters described in its opinion, the exchange ratio of 3.575 shares of American Tower Class A common stock for each share of SpectraSite common stock is fair, from a financial point of view, to American Tower. See the section captioned “—Opinion of American Tower’s Financial Advisor” beginning on page 42. A copy of Citigroup’s opinion, dated May 3, 2005, is attached as Annex B to this joint proxy statement/prospectus and is incorporated herein by reference.

•

The terms of the merger agreement relating to third-party offers, including:

•

the limitations on the ability of both parties to solicit offers for alternative business combinations; and

•

each party’s ability, under certain circumstances, to terminate the merger agreement in order to accept a superior proposal from a third party.

The American Tower board of directors weighed these advantages and opportunities against a number of other factors identified in its deliberations weighing negatively against the merger, including:

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The challenges inherent in the combination of two businesses of the size and scope of American Tower and SpectraSite and the possible diversion of management’s attention from ongoing business concerns.

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The risk of not capturing all the anticipated cost synergies between American Tower and SpectraSite relating to enhanced efficiencies and the risk that other anticipated benefits might not be realized.

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The possibility that the combined company may be unable to maximize its ability to take advantage of its diverse tower portfolio to create better opportunities with customers or improve current capital structure of American Tower.

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The potential risks associated with the combined company’s increased revenue concentration from the national wireless carriers as a result of the merger, in particular because a significant percentage of SpectraSite’s revenues are derived from Sprint PCS/Nextel and Cingular Wireless.

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Based solely on the realization of the expected cost synergies of the merger, the expectation that the merger would be dilutive to American Tower stockholders in the near-term on a per share basis.

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The requirement that American Tower consummate the merger regardless of whether it has obtained the requisite consents or waivers of SpectraSite’s lenders and note holders.

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The possibility of delay in obtaining antitrust approvals or the imposition of unfavorable terms by antitrust authorities, including the possibility that the combined company may be required to divest a significant amount of assets. See the section captioned “—Regulatory Matters” beginning on page 67.

After consideration of these factors, the American Tower board of directors determined that these risks were significantly outweighed by the potential benefits of the merger.

This discussion of the information and factors considered by the American Tower board of directors includes all of the material positive and negative factors considered by the American Tower board of directors, but it is not intended to be exhaustive and may not include all the factors considered by the American Tower board of directors. In reaching its determination to approve and recommend the merger agreement and the merger, the American Tower board of directors did not quantify or assign any relative or specific weights to the various factors that it considered in reaching its determination that the merger agreement and the merger are advisable and in the best interests of American Tower and its stockholders. Rather, the American Tower board of directors viewed its position and recommendation as being based on the totality of the information presented to, and factors considered by, it. In addition, individual members of the American Tower board of directors may have given differing weights to different factors.

Recommendation of American Tower’s Board of Directors

After careful consideration, the American Tower board of directors, on May 3, 2005, unanimously determined that the merger is consistent with and in furtherance of the long-term business strategy of American Tower and in the best interests of American Tower and its stockholders and approved and adopted the merger agreement, the merger and the other transactions contemplated by the merger agreement. The American Tower board of directors unanimously recommends that the stockholders of American Tower vote “FOR” the approval of the American Tower merger proposal.

Opinion of American Tower’s Financial Advisor

Citigroup Global Markets Inc. was retained to act as financial advisor to American Tower in connection with the merger. Pursuant to American Tower’s engagement letter with Citigroup, Citigroup rendered an opinion to the American Tower board of directors dated as of May 3, 2005, to the effect that, as of the date of the opinion, and based upon and subject to the considerations and limitations set forth in the opinion, Citigroup’s work

described below and other factors Citigroup deemed relevant, the exchange ratio was fair, from a financial point of view, to American Tower.

The full text of Citigroup’s opinion, which sets forth the assumptions made, general procedures followed, matters considered and limits on the review undertaken, is included as Annex B to this joint proxy statement/prospectus. The summary of Citigroup’s opinion set forth below is qualified in its entirety by reference to the full text of the opinion. You are urged to read Citigroup’s opinion carefully and in its entirety.

Citigroup’s opinion was limited solely to the fairness of the exchange ratio from a financial point of view as of the date of the opinion. Neither Citigroup’s opinion nor the related analyses constituted a recommendation of the merger to the American Tower board of directors. Citigroup makes no recommendation to any stockholder regarding how such stockholder should vote with respect to the merger.

In arriving at its opinion, Citigroup reviewed a draft of the merger agreement dated May 3, 2005 and held discussions with certain senior officers, directors and other representatives and advisors of American Tower and certain senior officers and other representatives and advisors of SpectraSite concerning the business, operations and prospects of American Tower and SpectraSite. Citigroup examined certain publicly available business and financial information relating to American Tower and SpectraSite as well as certain financial forecasts and other information and data relating to American Tower and SpectraSite and the industry in which they operate, which were provided to, or otherwise reviewed by or discussed with, Citigroup by the respective managements of American Tower and SpectraSite, including information relating to the potential strategic implications and operational benefits, including, the amount, timing and achievability thereof, anticipated by the managements of American Tower and SpectraSite to result from the merger. Citigroup reviewed the financial terms of the merger as set forth in the draft merger agreement reviewed by it in relation to, among other things:

•

current and historical market prices and trading volumes of American Tower Class A common stock and SpectraSite common stock;

•

the historical and projected earnings and other operating data of American Tower and SpectraSite; and

•

the capitalization and financial condition of American Tower and SpectraSite.

Citigroup considered, to the extent publicly available, the financial terms of certain other transactions that Citigroup considered relevant in evaluating the merger and analyzed certain financial, stock market and other publicly available information relating to the businesses of other companies whose operations Citigroup considered relevant in evaluating those of American Tower and SpectraSite. Citigroup also evaluated certain pro forma financial effects of the merger on American Tower. In addition to the foregoing, Citigroup conducted such other analyses and examinations and considered such other information and financial, economic and market criteria as Citigroup deemed appropriate in arriving at its opinion.

In rendering its opinion, Citigroup assumed and relied, without independent verification, upon the accuracy and completeness of all financial and other information and data publicly available or provided to or otherwise reviewed by or discussed with it and upon the assurances of the managements of American Tower and SpectraSite that they were not aware of any relevant information that had been omitted or remained undisclosed to Citigroup. With respect to financial forecasts and other information and data relating to American Tower, SpectraSite and the industry in which they operate provided to or otherwise reviewed by or discussed with it, Citigroup was advised by the respective managements of American Tower and SpectraSite that such forecasts and other information and data were reasonably prepared on bases reflecting the best currently available estimates and judgments of the managements of American Tower and SpectraSite as to the future financial performance of American Tower and SpectraSite and the industry in which they operate, the potential strategic implications and operational benefits anticipated to result from the merger and the other matters covered thereby, and Citigroup assumed, with the consent of the American Tower board of directors, that the financial results, including the potential strategic implications and operational benefits anticipated to result from the merger,

reflected in such forecasts and other information and data will be realized in the amounts and at the times projected. Citigroup assumed, with the consent of the American Tower board of directors, that the merger will be consummated in accordance with the terms of the merger agreement, without waiver, modification or amendment of any material term, condition or agreement and that, in the course of obtaining the necessary regulatory or third party approvals, consents and releases for the merger, no delay, limitation, restriction or condition will be imposed that would have an adverse effect on American Tower, SpectraSite or the contemplated benefits of the merger. Representatives of American Tower advised Citigroup, and Citigroup further assumed, that the final terms of the merger agreement would not vary materially from those set forth in the draft reviewed by it. Citigroup also assumed, with the consent of the American Tower board of directors, that the merger will be treated as a tax-free reorganization for federal income tax purposes.

Citigroup noted that its opinion relates to the relative values of American Tower and SpectraSite. Citigroup did not express any opinion as to what the value of the American Tower Class A common stock actually will be when issued pursuant to the merger or the price at which American Tower Class A common stock will trade at any time. Citigroup did not make and was not provided with an independent evaluation or appraisal of the assets or liabilities, contingent or otherwise, of American Tower and SpectraSite nor did Citigroup make any physical inspection of the properties or assets of American Tower and SpectraSite.

Citigroup expresses no view as to, and Citigroup’s opinion does not address, the relative merits of the merger as compared to any alternative business strategies that might exist for American Tower or the effect of any other transaction in which American Tower might engage. Citigroup’s opinion was necessarily based upon information available to it, and financial, stock market and other conditions and circumstances existing, as of the date of its opinion.

In connection with rendering its opinion, Citigroup made a presentation to the American Tower board of directors on May 2, 2005 with respect to the material analyses performed by Citigroup. On May 3, Citigroup orally updated the American Tower board of directors with respect to due diligence and the final exchange ratio agreed to by American Tower and SpectraSite and delivered the opinion attached hereto as Annex B. The following is a summary of the written presentation Citigroup delivered to the American Tower board of directors in connection with Citigroup’s May 2, 2005 presentation, updated to reflect the discussion of May 3, 2005. The summary includes information presented in tabular format. In order to understand fully the financial analyses used by Citigroup, these tables must be read together with the text of each summary. The tables alone do not constitute a complete description of the financial analyses. The following quantitative information, to the extent it is based on market data, is, except as otherwise indicated, based on market data as it existed at or prior to April 26, 2005, and is not necessarily indicative of current or future market conditions.

Historical Exchange Ratio Analysis. Citigroup calculated the implied current exchange ratio at April 26, 2005 by dividing the closing price per share of SpectraSite common stock by the closing price per share of American Tower Class A common stock on such date. Citigroup also calculated the high, low and average historical exchange ratios for the one-month, three-month, six-month and 12-month periods, in each case ending April 26, 2005. The results of this analysis are set forth below:


	High	Low	Average
April 26, 2005	3.28x	3.28x	3.28x
Preceding Month	3.39x	3.17x	3.26x
Preceding Three Months	3.40x	3.17x	3.29x
Preceding Six Months	3.40x	2.92x	3.21x
Preceding 12 Months	3.40x	2.75x	3.07x

Citigroup also calculated the one-month average historical exchange ratio assuming that certain synergies anticipated to result from the merger would be realized by the combined company following the merger, the benefits of which were allocated to SpectraSite. These synergy estimates, which were prepared by the

managements of American Tower and SpectraSite, consisted of a range of $29.0 to $36.0 million of anticipated annual run rate operating cost savings and Citigroup, with the consent of the American Tower board of directors, used $36.0 million of anticipated synergies in its analyses, which Citigroup refers to as the Anticipated Annual Synergies, or an aggregate of approximately $435.0 million in net present value of future anticipated synergies, which Citigroup refers to as the Anticipated Aggregate Synergy Value, assuming a 4% annual growth rate in perpetuity and a weighted average cost of capital of 8.75%. Taking the Anticipated Aggregate Synergy Value into account, Citigroup derived a one-month average implied historical exchange ratio for the merger of 3.74x.

Research Price Targets. Citigroup reviewed future price targets for the price per share of American Tower Class A common stock and SpectraSite common stock in Wall Street research reports published by selected financial analysts prior to April 26, 2005. Citigroup noted that the ranges of future price targets published by the selected financial analysts for each of American Tower and SpectraSite were $18.0 to $25.0 and $64.0 to $73.0, respectively. Citigroup added the Anticipated Aggregate Synergy Value per SpectraSite share to the selected financial analysts’ future price targets for SpectraSite in order to calculate the implied exchange ratios based on the high and low price targets. This analysis suggested exchange ratios from 3.26x to 4.02x.

Analysis of Trading Multiples. Citigroup derived certain trading multiples for each of American Tower, SpectraSite and selected tower industry companies that Citigroup deemed comparable to American Tower and SpectraSite, and compared the derived multiples to similar information for SpectraSite assuming consummation of the merger at the exchange ratio of 3.575x. The trading multiples considered by Citigroup in the course of this analysis were:

•

Firm value as multiple of pre-lease adjusted estimated earnings before interest, taxes, depreciation and amortization, which Citigroup refers to as EBITDA, for each of calendar years 2005 and 2006. For purposes of its analyses, Citigroup used earnings prior to adjustments for certain non-cash lease expenses relating to previously announced and disclosed accounting changes by American Tower and SpectraSite; and

•

Stock price as a multiple of estimated levered free cash flow, as defined below, per share for each of calendar years 2005 and 2006.

The comparable companies selected by Citigroup included Crown Castle International Corporation, Global Signal, Inc. and SBA Communications Corporation. Financial information and data for American Tower and SpectraSite used by Citigroup in the course of this analysis was based on projections provided to Citigroup by the managements of American Tower and SpectraSite, respectively. Financial information and data for the comparable companies used by Citigroup in the course of this analysis was based on information available in public documents and various equity research reports using the closing prices of each company’s common stock as of April 26, 2005. Citigroup defined firm value as the aggregate value of all shares of common stock, assuming the exercise of all in-the-money options, warrants and convertible securities outstanding, less the proceeds from such exercise, which Citigroup refers to as equity value, plus non-convertible indebtedness, non-convertible preferred stock, minority interest and out-of-the-money convertibles, minus investments in unconsolidated affiliates and cash and cash equivalents. Citigroup defined discretionary free cash flow as EBITDA minus maintenance capital expenditures, working capital, interest expense and cash taxes. Citigroup defined levered free cash flow as discretionary free cash flow minus non-maintenance capital expenditures and adjustments for all non-cash revenues and expenses. The results of this analysis are set forth below:


	Firm Value as a multiple of		Stock Price as a multiple of
	2005E EBITDA	2006E EBITDA	2005E Levered Free Cash Flow	2006E Levered Free Cash Flow
American Tower	15.1x	13.8x	21.3x	14.5x
SpectraSite	16.2x	14.6x	27.2x	20.8x
Comparable Companies Range	16.2x-18.2x	14.2x-17.1x	20.1x-27.9x	18.3x-19.3x
SpectraSite (at an exchange ratio of 3.575x and assuming Anticipated Annual Synergies)	15.0x	13.6x	22.1x	18.0x

Precedent REIT Transactions Premiums Analysis. Citigroup reviewed publicly available information for twenty-nine transactions involving real estate investment trusts, which Citigroup refers to as REITs, with transaction values in excess of $1.0 billion announced since 1996. Citigroup selected the REIT transactions for its premiums analysis because there were no comparable corporate transactions involving tower companies and because the tower and REIT businesses are both real estate based and the anticipated operating cost synergies resulting from such transactions are driven by savings in general, administrative and corporate expenses. The selected precedent transactions reviewed by Citigroup were:


Acquiror		Target
• Aptco LLC		• Berkshire Realty Co. Inc.
• Archstone Communities Trust.		• Charles E. Smith Residential
• Bay Apartment Communities Inc.		• Avalon Properties Inc.
• Calwest Industrial Property		• Cabot Industrial Trust
• Camden Property Trust		• Summit Properties Inc.
• Colonial Properties Trust		• Cornerstone Realty Income Trust
• Duke Realty Investments Inc.		• Weeks Corp.
• Equity Office Properties Trust		• Spieker Properties Inc.
• Equity Office Properties Trust		• Cornerstone Properties Inc.
• Equity Office Properties Trust		• Beacon Properties Corp.
• Equity Residential Property Trust		• Merry Land & Investment Co. Inc.
• Excel Realty Trust Inc.		• New Plan Realty Trust
• General Electric Capital Corp.		• Security Capital Group Inc.
• General Electric Capital Corp.		• Franchise Finance Corporation of America
• General Growth Properties Inc.		• Rouse Co.
• Heritage Property Investment Trust		• Bradley Real Estate Inc.
• Hometown America LLC		• Chateau Communities Inc.
• Irvine Co.		• Irvine Apartment Communities
• Olympus Real Estate Corp.		• Walden Residential Properties
• Pennsylvania Real Estate Investment		• Crown American Realty Trust
• Prologis Trust		• Meridian Industrial Trust Inc.
• Prologis, Inc.-Eaton Vance		• Keystone Property Trust
• Rodamco North America N.V.		• Urban Shopping Centers Inc.
• Security Capital Group Inc.		• Storage USA Inc.
• Security Capital Pacific Trust		• Security Capital Atlantic Inc.
• Simon Property Group Inc.		• Chelsea Property Group Inc.
• Simon Property Group Inc.		• DeBartolo Realty Corp.
• Starwood Financial Trust		• TriNet Corporate Realty Trust
• Westfield America Trust		• Westfield America, Inc.

For each of the selected REIT transactions noted above, Citigroup derived and compared with similar information for the merger the per share premium or discount paid or proposed to be paid to the target company’s shareholders based on the closing price per share of the target company’s common stock one day, one week and one month prior to the announcement of the transaction. With respect to financial information for the

precedent REIT transactions, Citigroup relied on information in publicly available documents and various equity research reports. The results of this analysis were as follows:


	Premium (Discount)
	One Day Prior		One Week Prior		One Month Prior
Low	(6.5	)%	(5.6	)%	(2.5	)%
Mean	15.1		15.6		17.4
Median	13.4		15.2		13.5
High	39.4		38.9		41.2

Citigroup noted that applying the mean and median one-month premiums to SpectraSite’s one-month average stock price implied exchange ratios of 3.70x and 3.83x, respectively.

Discounted Cash Flow Analyses. Citigroup performed several discounted cash flow analyses of each of American Tower and SpectraSite on a standalone basis by calculating for each of American Tower and SpectraSite the present value of estimated future unlevered free cash flow for the period from 2005 through the end of calendar year 2012 and adding to this amount the present value of each company’s respective estimated terminal values at the end of calendar year 2012. Citigroup defined unlevered free cash flow as levered free cash flow excluding costs related to debt servicing. Forecasted financial information for American Tower and SpectraSite for 2005 through 2012 used by Citigroup in the course of this analysis was based on estimates provided by the managements of American Tower and SpectraSite. Citigroup analyzed the following business cases:

•

estimates of the future financial performance of American Tower and SpectraSite provided to Citigroup by the managements of American Tower and SpectraSite, respectively, which Citigroup refers to as the Management Cases;

•

the Management Cases with the Anticipated Aggregate Synergy Value allocated to SpectraSite;

•

the Management Cases with the Anticipated Aggregate Synergy Value allocated to SpectraSite, adjusted such that SpectraSite’s standalone incremental annual revenue represented 90% of American Tower’s standalone incremental U.S. annual revenue from 2008 through 2012, which Citigroup refers to as the 90% Case; and

•

the Management Cases with the Anticipated Aggregate Synergy Value allocated to SpectraSite, adjusted such that SpectraSite’s standalone incremental annual revenue represented 60% of American Tower’s standalone incremental U.S. annual revenue from 2007 through 2012, which Citigroup refers to as the 60% Case.

American Tower management advised Citigroup, and Citigroup assumed with the consent of the American Tower board of directors, that the 90% Case represented the best estimate as to SpectraSite’s future performance. For purposes of this analysis, Citigroup used ranges for the weighted average cost of capital for American Tower and SpectraSite of 8.9% to 9.9% and 8.3% to 9.3%, respectively. Citigroup used perpetuity growth rates ranging from 3.5% to 4.5% for both American Tower and SpectraSite. The results of this analysis are set forth below:


		Midpoint of Implied Exchange Ratio Range
Management Case		3.84x
Management Case with Anticipated Aggregate Synergy Value		4.28x
90% Case		3.67x
60% Case		3.12x

Contribution Analysis. Citigroup reviewed certain historical and estimated future operating, financial and market information for American Tower and SpectraSite, and the relative contribution of American Tower to the

combined company taking into account each of American Tower’s and SpectraSite’s existing indebtedness. The information used by Citigroup in the course of this analysis was based on publicly available financial information and estimates provided by the respective managements of American Tower and SpectraSite. In evaluating the discretionary free cash flows and free cash flows, Citigroup assumed conversion of in-the-money convertible notes.

The results of this analysis are set forth below:


Metric		Levered American Tower Contribution
Towers
2006 Estimated		59%
Revenues
2006 Estimated		60%
EBITDA
2006 Estimated		63%
2006 Estimated (assuming Anticipated Annual Synergies)		59%
Discretionary Free Cash Flow
2006 Estimated		65%
2006 Estimated (assuming Anticipated Annual Synergies)		61%
Levered Free Cash Flow
2006 Estimated		70%
2006 Estimated (assuming Anticipated Annual Synergies)		64%
Equity Value
At market		62%
SpectraSite at the exchange ratio of 3.575x		59%

Accretion/Dilution Analysis. Citigroup analyzed and considered the impact of the merger on each of American Tower and SpectraSite by comparing the combined company’s projected discretionary free cash flow and levered free cash flow in each of 2005 through 2008, assuming that the combined company would achieve the Anticipated Annual Synergies, to similar information for American Tower and SpectraSite on a standalone basis. Citigroup further determined the amount of additional cash flow the combined company would need in each year, 2005 through 2008, to offset the potential dilution, which Citigroup refers to as the Uplift. Financial information for each of American Tower and SpectraSite was based on Management Cases. For purposes of this analysis, discretionary free cash flow and levered free cash flow exclude non-recurring charges related to the merger. The following table summarizes the results of this analysis:


	American Tower Accretion/(Dilution)		Uplift (in millions)
Discretionary Free Cash Flow
2005	(4.1	)%	$	19.0
2006	(2.4	)%	$	15.0
2007	(0.8	)%	$	6.0
2008	1.5	%		N/A

Levered Free Cash Flow
2005	(6.3	)%	$	23.0
2006	(7.7	)%	$	41.0
2007	(6.4	)%	$	41.0
2008	(2.8	)%	$	22.0

Citigroup’s advisory services and opinion were provided for the information of the American Tower board of directors in its evaluation of the merger and did not constitute a recommendation of the merger to American Tower or a recommendation to any person as to how such person should vote on any matters relating to the merger.

The preceding discussion is a summary of the material financial analyses furnished by Citigroup to the American Tower board of directors, but it does not purport to be a complete description of the analyses performed by Citigroup or of its presentation to the American Tower board of directors. The preparation of financial analyses and fairness opinions is a complex process involving subjective judgments and is not necessarily susceptible to partial analysis or summary description. Citigroup made no attempt to assign specific weights to particular analyses or factors considered, but rather made qualitative judgments as to the significance and relevance of all the analyses and factors considered and determined to give its fairness opinion as described above. Accordingly, Citigroup believes that its analyses, and the summary set forth above, must be considered as a whole, and that selecting portions of the analyses and of the factors considered by Citigroup, without considering all of the analyses and factors, could create a misleading or incomplete view of the processes underlying the analyses conducted by Citigroup and its opinion. With regard to the comparable companies and precedent transaction analyses summarized above, Citigroup selected comparable public companies and precedent transactions on the basis of various factors, including size and similarity of the line of business of the relevant entities; however, no company utilized in this analysis is identical to American Tower and SpectraSite and no precedent transaction is identical to the merger. As a result, this analysis is not purely mathematical, but also takes into account differences in financial and operating characteristics of the subject companies and other factors that could affect the transaction or the public trading value of the subject companies to which American Tower and SpectraSite are being compared.

In its analyses, Citigroup made numerous assumptions with respect to American Tower, SpectraSite, industry performance, general business, economic, market and financial conditions and other matters, many of which are beyond the control of American Tower and SpectraSite. Any estimates contained in Citigroup’s analyses are not necessarily indicative of actual values or predictive of future results or values, which may be significantly more or less favorable than those suggested by these analyses. Estimates of values of companies do not purport to be appraisals or necessarily to reflect the prices at which companies may actually be sold. Because these estimates are inherently subject to uncertainty, none of American Tower, SpectraSite, the American Tower board of directors, the SpectraSite board of directors, Citigroup or any other person assumes responsibility if future results or actual values differ materially from the estimates.

Citigroup’s analyses were prepared solely as part of Citigroup’s analysis of the fairness of the exchange ratio and were provided to the American Tower board of directors in that connection. The opinion of Citigroup was only one of the factors taken into consideration by the American Tower board of directors in making its determination to approve the merger agreement and the merger. See the section captioned “ —American Tower’s Reasons for the Merger” beginning on page 40.

Citigroup is an internationally recognized investment banking firm engaged in, among other things, the valuation of businesses and their securities in connection with mergers and acquisitions, restructurings, leveraged buyouts, negotiated underwritings, competitive biddings, secondary distributions of listed and unlisted securities, private placements and valuations for estate, corporate and other purposes. American Tower selected Citigroup to act as its financial advisor to the board of directors of American Tower in connection with the proposed merger on the basis of Citigroup’s international reputation.

Citigroup was retained by American Tower in connection with the merger in March 2005. Citigroup entered into an engagement letter with American Tower dated as of May 3, 2005 pursuant to which American Tower has agreed to pay Citigroup (1) $15.0 million payable upon the consummation of the merger or (2) in the event that American Tower becomes entitled to any termination fee within twelve months of the date of the engagement

letter, a fee equal to 20%, capped at $15.0 million, of all such termination fees subject to adjustments based on costs incurred by American Tower in collecting the termination fee. American Tower has also agreed to indemnify Citigroup against specific liabilities and expenses relating to or arising out of its engagement, including liabilities under the federal securities laws. Citigroup and its affiliates have in the past provided services to American Tower and SpectraSite unrelated to the proposed merger, for which services Citigroup and such affiliates has received compensation, including, without limitation, by acting as lead-manager, co-manager or bookrunner in connection with certain transactions by American Tower, and acting as joint bookrunner, co-manager or syndicate agent in connection with certain transactions by SpectraSite, in each case since 2003. Citigroup and certain of its affiliates may provide financing to American Tower in connection with the merger. In the ordinary course of its business, Citigroup and its affiliates may actively trade or hold the securities of American Tower and SpectraSite for its own account or for the account of its customers and, accordingly, may at any time hold a long or short position in such securities. In addition, Citigroup and its affiliates, including Citigroup Inc. and its affiliates, may maintain relationships with American Tower, SpectraSite and their respective affiliates.

SpectraSite’s Reasons for the Merger

In reaching its conclusion to approve the merger, the SpectraSite board of directors consulted with SpectraSite’s management team, as well as SpectraSite’s outside consultants, financial advisors and legal counsel, and the SpectraSite board of directors made the following principal observations as to this matter:

•

The ability of the combined company following the merger to compete more effectively than SpectraSite on a standalone basis in the wireless communications tower industry would be substantially enhanced over the long term as a result of the increased size, geographic reach, financial strength and expanded access to capital markets of the combined company and by the greater capacity of the combined company to satisfy the needs of its wireless carrier customers.

•

American Tower’s strategic fit with SpectraSite as a result of its existing position in the wireless communications tower industry, relative size, long-term strategic direction, prospects for growth and management capability make it a very attractive merger candidate for SpectraSite.

•

A merger with American Tower would have the potential to produce cost savings primarily resulting from anticipated lower selling, general and administrative costs, reduced operating expenses and elimination of duplicative corporate functions.

•

The advantage of being one of the first substantial business combinations in what the SpectraSite board of directors believes to be the likely consolidation of the wireless communications tower industry. The SpectraSite board of directors considered current industry, economic and market conditions and trends in the telecommunications industry, including the recent consolidation and increased competition among wireless carriers. Based on the belief of the SpectraSite board of directors that consolidation in the wireless communications tower industry is likely in response to wireless carrier consolidation, the SpectraSite board of directors also considered the expected decrease with the passage of time in the number of suitable strategic partners for SpectraSite leaving SpectraSite with fewer opportunities to achieve relevant scale through acquisitions or business combinations.

•

The fact that the exchange ratio of 3.575x to be received by the holders of SpectraSite common stock in the merger represents a premium of approximately 11% over the exchange ratio between the closing prices of American Tower Class A common stock and SpectraSite common stock on May 2, 2005, the last trading day before the meeting of the SpectraSite board of directors and premiums of approximately 10%, 9%, 10%, 11% and 16%, respectively, over the average exchange ratio between American Tower Class A common stock and SpectraSite common stock during the 30 trading days, 60 trading days, 90 trading days, six months and one year periods ended May 2, 2005, respectively.

•

The financial terms of the merger offered to the holders of SpectraSite common stock were fair and the other terms of the merger outlined in the merger agreement were reasonable.

In weighing the relative merits of the merger, the SpectraSite board of directors considered the following principal factors as generally supporting its decision to approve the merger agreement and the merger:

•

The SpectraSite board of directors’ consideration of possible business combinations and other strategic alternatives, as described further under the section captioned “—Background of the Merger,” including the process undertaken by the Strategy Committee of the SpectraSite board of directors, with the assistance of SpectraSite’s management, outside consultants, legal counsel and financial advisors, to explore and review long-term strategic alternatives in the best interests of SpectraSite stockholders.

•

The SpectraSite board of directors’ understanding of economic and industry conditions relating to the wireless communications tower industry, including SpectraSite’s prospects on a standalone basis in light of recent wireless carrier consolidation, which the SpectraSite board of directors believes presents greater risk to SpectraSite on a standalone basis than to the combined company after the merger.

•

The business, operations, financial condition, cash flow and prospects of American Tower on a standalone basis and forecasted for the combined company after the merger.

•

The then-current financial market conditions and historical market prices, volatility and trading information with respect to shares of SpectraSite common stock and American Tower Class A common stock.

•

Both Lehman Brothers Inc. and Evercore Group Inc., on May 3, 2005, delivered a presentation containing financial analysis and rendered oral opinions, subsequently confirmed in writing, to the SpectraSite board of directors, stating that, as of that date, and based on and subject to the assumptions made, matters considered, and limitations on and qualifications made by each of Lehman Brothers and Evercore in its review, the exchange ratio to be offered to the holders of SpectraSite common stock in connection with the merger is fair, from a financial point of view, to the holders of SpectraSite’s common stock. See the section captioned “—Opinions of SpectraSite’s Financial Advisors” beginning on page 53. Copies of Lehman Brothers’ and Evercore’s written opinions, each dated May 3, 2005, are attached as Annex C and Annex D, respectively, to this joint proxy statement/prospectus and are incorporated by reference herein.

•

The terms and conditions of the merger agreement, including the parties’ representations, warranties, covenants and agreements, and the conditions to their respective obligations, as well as the manageable execution risk of consummating the merger, the proposed structure of the transaction, the attractive operational and capital market profile of the combined company following the merger and the anticipated closing date of the merger are favorable for a transaction of this size and nature.

•

The level of efforts that the parties must use under the merger agreement to obtain governmental and regulatory approvals, and the SpectraSite board of directors’ belief, after review with outside legal counsel, in the likelihood of the merger being approved by the appropriate regulatory authorities in light of these merger agreement provisions. See the section captioned “ —Regulatory Matters” beginning on page 67.

•

The termination, no-shop and break-up fee provisions of the merger agreement, which the SpectraSite board of directors determined, based in part on advice from SpectraSite’s outside legal counsel, were generally typical for a transaction of the magnitude of the merger and would not unduly inhibit alternative merger or acquisition proposals.

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The ability to consummate the merger as a reorganization for U.S. federal income tax purposes, which supported the merger in that the transaction would not be taxable to the companies and the stock consideration to be received would not be taxable to SpectraSite’s common stockholders.

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The benefits to former SpectraSite stockholder interests through the addition of four of the existing SpectraSite directors to the board of directors of American Tower at the effective time of the merger.

•

The results of due diligence investigations of American Tower by SpectraSite’s management, independent auditors, outside legal counsel and financial advisors.

As discussed more specifically below, the considerations favoring pursuit of a business combination rather than a standalone strategy were analyzed in the context of potentially adverse consequences of the merger, particularly the difficulty involved in integrating two large organizations and the risk that expected synergies would not be realized. In this regard, the SpectraSite board of directors considered the following potentially adverse consequences to SpectraSite, its common stockholders and the combined company that could arise from pursuing the merger:

•

The risk that anticipated synergies and cost savings will not be achieved.

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The challenges of integrating the assets and operations of two large companies and risks of diverting the attention of SpectraSite management from other strategic initiatives while focusing on consummation of the merger and post-closing integration.

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The possibility that SpectraSite’s and American Tower’s businesses would be adversely affected during the period from signing the merger agreement until integration is substantially implemented by competitive pressures and the disruption inherent in combining two large businesses.

•

The timing and receipt of governmental and regulatory approvals for the merger, and the possibility that delays in obtaining regulatory approvals of the merger could delay the closing or a significant amount of assets of the combined company could be required to be divested.

•

If, once initiated, the merger is not ultimately consummated, this fact could have the effect of depressing values offered by others to SpectraSite in a business combination and could erode customer and employee confidence in SpectraSite.

•

The fact that stockholder approval of the transaction would be required from both SpectraSite and American Tower.

•

The interest of SpectraSite’s executive officers and directors with respect to the merger may be different from, or in addition to, the interests of SpectraSite’s common stockholders, as described in the section captioned “—Conflicts of Interests of SpectraSite Directors and Executive Officers in the Merger” beginning on page 63.

After consideration of these material factors, the SpectraSite board of directors determined that these risks are of the nature that are customary in business combinations similar to the merger, could be mitigated or managed by SpectraSite or American Tower or by American Tower following the merger, were reasonably acceptable under the circumstances, or, in light of the anticipated benefits, the risks were unlikely to have a material impact on the merger or on American Tower following the merger, and that, overall, these risks were significantly outweighed by the potential benefits of the merger.

This discussion of the information and factors considered by the SpectraSite board of directors is not intended to be exhaustive but includes the material factors considered by the SpectraSite board of directors. In view of the wide variety of factors considered in connection with its evaluation of the merger and the complexity of these matters, the SpectraSite board of directors did not find it useful to and did not attempt to quantify, rank or otherwise assign relative weights to these factors. In addition, the SpectraSite board of directors did not undertake to make any specific determination as to whether any particular factor, or any aspect of any particular factor, was favorable or unfavorable to its ultimate determination, but rather the SpectraSite board of directors conducted an overall analysis of the factors described above, including discussions with SpectraSite’s management, outside consultants, legal counsel and financial advisors. In considering the factors described above, individual members of the SpectraSite board of directors may have given different weight to different

factors. It should be noted that this explanation of the reasoning of the SpectraSite board of directors and certain information presented in this section is forward-looking in nature and, therefore, such information should be read in light of the factors discussed in the section captioned “STATEMENT REGARDING FORWARD-LOOKING INFORMATION” beginning on page 116.

Recommendation of SpectraSite’s Board of Directors

After careful consideration, the SpectraSite board of directors, on May 3, 2005, unanimously determined that the merger is consistent with and in furtherance of the long-term business strategy of SpectraSite and in the best interest of SpectraSite and its stockholders, and approved and adopted the merger agreement, including the merger and the other transactions contemplated thereby. The SpectraSite board of directors unanimously recommends that the stockholders of SpectraSite vote “FOR” the approval of the SpectraSite merger proposal.

In considering the recommendation of the SpectraSite board of directors with respect to the merger agreement, the SpectraSite stockholders should be aware that some of SpectraSite’s directors and executive officers will receive benefits if the merger is consummated, which results in those persons having interests in the merger that are different from, or are in addition to, the interests of SpectraSite stockholders. See the section captioned “—Conflicts of Interests of SpectraSite Directors and Executive Officers in the Merger” beginning on page 63.

Opinions of SpectraSite’s Financial Advisors

Opinion of Lehman Brothers Inc. Lehman Brothers acted as financial advisor to SpectraSite in connection with the American Tower merger and, on May 3, 2005, delivered its oral opinion, subsequently confirmed in writing, to the SpectraSite board of directors that as of such date and, based upon and subject to the matters stated in its opinion, the exchange ratio in the merger was fair to SpectraSite stockholders from a financial point of view.

The full text of Lehman Brothers’ written opinion, dated May 3, 2005, is attached as Annex C to this joint proxy statement/prospectus. SpectraSite stockholders are encouraged to read Lehman Brothers’ opinion carefully in its entirety for a description of the assumptions made, procedures followed, factors considered and limitations upon the review undertaken by Lehman Brothers in rendering its opinion. The following is a summary of Lehman Brothers’ opinion and the methodology used to render its opinion. This summary is qualified in its entirety by reference to the full text of the opinion.

Lehman Brothers’ advisory services and opinion were provided for the information and assistance of the SpectraSite board of directors in connection with its consideration of the merger. Lehman Brothers’ opinion is not intended to be and does not constitute a recommendation to any stockholder of SpectraSite as to how such stockholder should vote in connection with the merger. Lehman Brothers was not requested to opine as to, and Lehman Brothers’ opinion does not address, SpectraSite’s underlying business decision to proceed with or effect the merger.

In arriving at its opinion, Lehman Brothers reviewed and analyzed, among other things:

•

the merger agreement and the specific terms of the merger;

•

publicly available information concerning SpectraSite and American Tower that Lehman Brothers believed to be relevant to its analysis, including SpectraSite’s and American Tower’s Annual Reports on Form 10-K for the fiscal year ended December 31, 2004;

•

financial and operating information with respect to the business, operations and prospects of SpectraSite furnished to Lehman Brothers by SpectraSite, including financial projections for 2005 through 2009 prepared by the management of SpectraSite, which Lehman Brothers refers to as the SpectraSite Projections;

•

financial and operating information with respect to the business, operations and prospects of American Tower furnished to Lehman Brothers by American Tower, including financial projections for 2005 through 2009 prepared by the management of American Tower, which Lehman Brothers refers to as the American Tower Projections;

•

trading histories of SpectraSite common stock and of American Tower Class A common stock from April 30, 2004 through May 2, 2005, and a comparison of these trading histories with each other and those of other companies that Lehman Brothers deemed relevant;

•

a comparison of the historical financial results and present financial condition of SpectraSite and American Tower with each other and with those of other companies that Lehman Brothers deemed relevant;

•

published estimates of third party research analysts with respect to the future financial performance of each of SpectraSite and American Tower;

•

a comparison of the financial terms of the merger with the financial terms of certain other recent transactions that Lehman Brothers deemed relevant;

•

the pro forma contribution of cash flows from operations that each of American Tower and SpectraSite would contribute to the combined company following the consummation of the merger; and

•

the pro forma impact of the merger on the balance sheet and future financial performance of American Tower, including the leverage, cost savings and operating synergies expected by the managements of SpectraSite and American Tower to result from the combination of the businesses of SpectraSite and American Tower, which Lehman Brothers refers to as the Expected Synergies.

In addition, Lehman Brothers had discussions with the managements of SpectraSite and American Tower concerning their respective businesses, operations, assets, financial conditions and prospects and undertook such other studies, analyses and investigations as Lehman Brothers deemed appropriate.

In arriving at its opinion, Lehman Brothers assumed and relied upon the accuracy and completeness of the financial and other information used by Lehman Brothers without assuming any responsibility for independent verification of such information and further relied upon the assurances of the managements of SpectraSite and American Tower that they were not aware of any facts or circumstances that would make such information inaccurate or misleading. With respect to the SpectraSite Projections, upon advice of SpectraSite, Lehman Brothers assumed that such projections were reasonably prepared on a basis reflecting the best currently available estimates and good faith judgments of the management of SpectraSite as to the future financial performance of SpectraSite and that SpectraSite would perform substantially in accordance with such projections. With respect to the American Tower Projections, upon advice of American Tower and SpectraSite, Lehman Brothers assumed that such projections were reasonably prepared on a basis reflecting the best currently available estimates and good faith judgments of the management of American Tower as to the future financial performance of American Tower and that American Tower would perform substantially in accordance with such projections. Upon the advice of SpectraSite, Lehman Brothers assumed that the amount and timing of the Expected Synergies were reasonable and the Expected Synergies will be realized substantially in accordance with such estimates. Lehman Brothers further assumed, upon advice of SpectraSite, that all material governmental, regulatory or other consents or approvals necessary for the consummation of the merger will be obtained within the constraints contemplated by the merger agreement. In arriving at its opinion, Lehman Brothers did not conduct a physical inspection of the properties and facilities of SpectraSite and American Tower and did not make or obtain any evaluations or appraisals of the assets or liabilities of SpectraSite or American Tower. Lehman Brothers’ opinion was necessarily based upon market, economic and other conditions as they existed on, and could be evaluated as of, May 3, 2005. In addition, Lehman Brothers expressed no opinion as to the prices at which (1) shares of SpectraSite common stock would trade at any time following the announcement of the merger or (2) shares of American Tower Class A common stock would trade at any time following the announcement or the consummation of the merger.

The following is a summary of the material financial analyses used by Lehman Brothers in connection with providing its opinion to the SpectraSite board of directors. The financial analyses summarized below include information presented in tabular format. In order to fully understand the financial analyses used by Lehman Brothers, the tables must be read together with the text of each summary. Considering any portion of such analyses and of the factors considered, without considering all analyses and factors, could create a misleading or incomplete view of the process underlying Lehman Brothers’ opinion.

Lehman Brothers is an internationally recognized investment banking firm and, as part of its investment banking activities, is regularly engaged in the valuation of businesses and their securities in connection with mergers and acquisitions, negotiated underwritings, competitive bids, secondary distributions of listed and unlisted securities, private placements and valuations for corporate and other purposes. The SpectraSite board of directors selected Lehman Brothers because of its expertise, reputation and familiarity with SpectraSite and the wireless communications tower industry generally and because its investment banking professionals have substantial experience in transactions comparable to the merger.

As compensation for its services in connection with the merger, SpectraSite paid Lehman Brothers $1.0 million upon the delivery of Lehman Brothers’ opinion. Compensation of $8.0 million will be payable on consummation of the merger against which the amounts paid for the opinion will be credited. In addition, SpectraSite has agreed to reimburse Lehman Brothers for reasonable out-of-pocket expenses incurred in connection with the merger and to indemnify Lehman Brothers for certain liabilities that may arise out of its engagement by SpectraSite and the rendering of the Lehman Brothers’ opinion. Lehman Brothers in the past has rendered and in the future may render investment banking services to SpectraSite, American Tower and their affiliates and has received and may receive customary fees for such services.

In the ordinary course of its business, Lehman Brothers may actively trade in the debt or equity securities of SpectraSite and American Tower for its own account and for the accounts of its customers and, accordingly, may at any time hold a long or short position in such securities.

Opinion of Evercore Group Inc. Evercore has acted as SpectraSite’s financial advisor in connection with the merger. In connection with Evercore’s engagement, the SpectraSite board of directors requested that Evercore render an opinion with respect to the fairness, from a financial point of view, to holders of shares of SpectraSite common stock, of the exchange ratio. At the meeting of the SpectraSite board of directors on May 3, 2005, Evercore rendered its oral opinion, which was subsequently confirmed in writing dated as of the same date, that, based upon and subject to the matters described in its opinion, the exchange ratio was fair, from a financial point of view, to the holders of shares of SpectraSite common stock.

The full text of Evercore’s opinion, dated May 3, 2005, which sets forth, among other things, the procedures followed, matters considered and limitations of the review undertaken in connection with its opinion, is attached as Annex D to this joint proxy statement/prospectus and is incorporated herein by reference. The summary of Evercore’s fairness opinion set forth in this joint proxy statement/prospectus is qualified in its entirety by reference to the full text of the opinion. Stockholders should read the opinion carefully and in its entirety.

Evercore’s opinion is directed to the board of directors of SpectraSite, addresses only the fairness, from a financial point of view, to holders of SpectraSite common stock of the exchange ratio and does not address any other aspect or implication of the merger or any other agreement, arrangement or understanding entered into in connection with the merger or otherwise. Evercore’s opinion does not constitute a recommendation to any stockholder of SpectraSite as to how such stockholder should vote or act with respect to any matter relating to the merger.

In arriving at its opinion, Evercore, among other things:

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reviewed a draft of the merger agreement dated May 3, 2005, which Evercore assumed was in substantially final form and would not vary in any respect material to its analysis;

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analyzed certain publicly available financial statements and other publicly available business information relating to SpectraSite and American Tower that Evercore deemed relevant, including but not limited to filings such as SpectraSite’s and American Tower’s respective Annual Reports on Form 10-K for the fiscal year ended December 31, 2004;

•

analyzed certain internal non-public financial and operating data concerning SpectraSite and American Tower prepared and furnished to Evercore by members of the management of SpectraSite and American Tower, respectively, and members of the management of SpectraSite provided Evercore with, and reviewed with Evercore, the estimated amount and timing of the Expected Synergies;

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analyzed certain financial projections concerning SpectraSite and American Tower furnished to Evercore by members of the management of SpectraSite and American Tower, including the American Tower Projections and the SpectraSite Projections;

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reviewed the reported prices and trading activity of the American Tower Class A common stock and SpectraSite common stock from April 30, 2004 to May 2, 2005, and a comparison of these trading histories with each other and those of other companies Evercore believed to be relevant;

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compared the historical financial results and present financial condition of SpectraSite and American Tower with those of other companies that Evercore believed to be relevant;

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reviewed published estimates of third party research analysts with respect to the future financial performance of each of SpectraSite and American Tower;

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compared the proposed financial terms of the merger with publicly available financial terms of certain business combination transactions that Evercore deemed relevant;

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analyzed the pro forma contribution of cash flows from operations that each of SpectraSite and American Tower would contribute to the combined company following the consummation of the transactions contemplated by the merger agreement;

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considered the potential pro forma impact of the merger on American Tower, based on inputs and analysis provided by members of the management of SpectraSite and American Tower; and

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had discussions with members of the management of SpectraSite and American Tower concerning their respective businesses, operations, assets, financial condition and prospects and undertook such other studies, analyses and investigations as Evercore deemed appropriate.

For purposes of its analyses and opinion, Evercore relied upon and assumed, without assuming any responsibility for independently verifying, the accuracy and completeness of all the financial and other information that was publicly available or was furnished to it by American Tower or SpectraSite or otherwise discussed with or reviewed by or for Evercore, and it has not assumed any liability therefor. Evercore further relied upon the assurances of members of the management of SpectraSite and American Tower that they are not aware of any facts that would make such information inaccurate or misleading. Evercore has not made nor assumed any responsibility for making any valuation or appraisal of any assets or liabilities of SpectraSite or American Tower, nor have any such valuations or appraisals been provided to Evercore, nor has Evercore evaluated the solvency of SpectraSite or American Tower under any state or federal laws relating to bankruptcy, insolvency or similar matters. With respect to the American Tower Projections, upon advice of SpectraSite, Evercore assumed that such projections have been reasonably prepared on a basis reflecting the best currently available estimates and good faith judgments of members of the management of American Tower as to the future financial performance of American Tower and that American Tower would perform on a stand-alone basis substantially in accordance with such projections. With respect to the SpectraSite Projections, Evercore assumed that such projections were reasonably prepared on a basis reflecting the best currently available estimates and good faith judgments of members of the management of SpectraSite as to the future financial performance of SpectraSite and that SpectraSite would perform on a stand-alone basis substantially in accordance with such

projections. With respect to the Expected Synergies, Evercore assumed that the timing and amounts of such Expected Synergies were reasonable and that the Expected Synergies would be realized substantially in accordance with such estimates. Evercore further assumed that neither the expenses associated with realizing the Expected Synergies nor expenses incurred in connection with the transactions contemplated by the merger agreement would be in an amount material to American Tower after giving effect to the merger. Evercore expressed no view as to such financial analyses and forecasts, the Expected Synergies or the assumptions on which they were based. Evercore also assumed that the merger will qualify as a tax-free reorganization for United States federal income tax purposes, and that the other transactions contemplated by the merger agreement would be consummated as described in the merger agreement. Evercore also assumed that the representations and warranties of each party contained in the merger agreement were true and correct, that each party would perform all of the covenants and agreements required to be performed by it under the merger agreement and that the merger would be consummated without waiver of any material terms or conditions set forth in the merger agreement. Evercore further assumed that all material governmental, regulatory or other consents and approvals necessary for the consummation of the merger would be obtained without adverse effect on SpectraSite or American Tower or on the contemplated benefits of the merger in any way meaningful to Evercore’s analysis.

Evercore’s opinion was necessarily based on economic, market and other conditions as in effect on, and the information made available to it as of, May 3, 2005. It should be understood that subsequent developments may affect Evercore’s opinion and that Evercore does not have any obligation to update, revise, or reaffirm its opinion. In connection with the merger, Evercore was not authorized to solicit, nor did it solicit, third party indications of interest for the acquisition of all or any part of SpectraSite or SpectraSite common stock. Evercore’s opinion was limited to the fairness, from a financial point of view, of the exchange ratio to the holders of SpectraSite common stock and it expressed no opinion as to the underlying decision by SpectraSite and American Tower to engage in the merger. Evercore expressed no opinion as to the price at which SpectraSite common stock or American Tower Class A common stock would trade at any future time.

On January 25, 2005, SpectraSite engaged Evercore to act as a financial advisor based on its qualifications, experience and reputation and its knowledge of the business of SpectraSite. Evercore is an internationally recognized investment banking firm and is regularly engaged in the valuation of businesses in connection with mergers and acquisitions, leveraged buyouts, competitive biddings, private placements and valuations for corporate and other purposes.

As compensation for its services in connection with the merger, SpectraSite paid Evercore $1.0 million upon the delivery of Evercore’s opinion. Compensation of $8.0 million will be payable on consummation of the merger against which the amounts paid for the opinion will be credited. In addition, SpectraSite has agreed to indemnify Evercore and its members, partners, officers, directors, advisors, representatives, employees, agents, affiliates and controlling persons, if any, against certain liabilities and expenses, including certain liabilities under the federal securities laws, related to or arising out of Evercore’s engagement and any related transactions. Michael J. Price, a Senior Managing Director of Evercore, was a member of the SpectraSite board of directors between April 1999 and August 2002.

Lehman Brothers’ and Evercore’s Analysis

Financial Analyses. In connection with the review of the merger by the SpectraSite board of directors, Lehman Brothers and Evercore performed a variety of financial and comparative analyses for purposes of rendering their opinions. The preparation of a fairness opinion is a complex process and is not necessarily susceptible to partial analysis or summary description. In arriving at their opinions, Lehman Brothers and Evercore considered the results of all of their analyses as a whole and did not attribute any particular weight to any analysis or factor considered by them. Furthermore, Lehman Brothers and Evercore believe that the summary provided and the analyses described below must be considered as a whole and that selecting any portion of their analyses, without considering all of them, would create an incomplete view of the process underlying their

analyses and opinions. In addition, Lehman Brothers and Evercore may have given various analyses and factors more or less weight than other analyses and factors and may have deemed various assumptions more or less probable than other assumptions, so that the ranges of valuations resulting from any particular analysis described above should not be taken to be Lehman Brothers’ and Evercore’s views of the actual value of SpectraSite or American Tower.

In performing their analyses, Lehman Brothers and Evercore made numerous assumptions with respect to industry risks associated with industry performance, general business and economic conditions and other matters, many of which are beyond the control of SpectraSite or American Tower. Any estimates contained in Lehman Brothers’ and Evercore’s analyses are not necessarily indicative of future results or actual values, which may be significantly more or less favorable than those suggested by such estimates. The analyses performed were prepared solely as part of Lehman Brothers’ and Evercore’s analyses of the fairness from a financial point of view to the holders of SpectraSite common stock of the 3.575x exchange ratio and were prepared in connection with the delivery by Lehman Brothers and Evercore of their opinions, each dated May 3, 2005, to the SpectraSite board of directors. The analyses do not purport to be appraisals or to reflect the prices at which SpectraSite common stock or American Tower Class A common stock might trade following announcement of the merger or the prices at which American Tower Class A common stock might trade following consummation of the merger.

Lehman Brothers and Evercore assumed that the terms of the merger were determined through arm’s length negotiations between SpectraSite and American Tower and were unanimously approved by the SpectraSite and American Tower boards of directors. Lehman Brothers and Evercore did not recommend any specific exchange ratio or form of consideration to SpectraSite or that any specific exchange ratio or form of consideration constituted the only appropriate consideration for the merger. Lehman Brothers’ and Evercore’s opinions were provided to the SpectraSite board of directors to assist it in its consideration of the exchange ratio in the merger. Lehman Brothers’ and Evercore’s opinions do not address any other aspect of the merger and do not constitute a recommendation to any stockholder as to how to vote or to take any other action with respect to the merger. Lehman Brothers’ and Evercore’s opinions were among the many factors taken into consideration by the SpectraSite board of directors in making its unanimous determination to approve the merger agreement. Lehman Brothers’ and Evercore’s analyses summarized below should not be viewed as determinative of the opinion of the SpectraSite board of directors with respect to the value of SpectraSite or American Tower or of whether the SpectraSite board of directors would have been willing to agree to a different exchange ratio or form of consideration.

Historical Share Price Analysis. Lehman Brothers and Evercore considered historical data with regard to the trading prices of SpectraSite and American Tower common stock for the period from April 30, 2004 to May 2, 2005, the last trading day prior to the delivery of Lehman Brothers’ and Evercore’s opinions, and the relative stock price performances during this same period of SpectraSite, American Tower, and the Standard & Poor’s 500 Index. During this period the closing stock price of SpectraSite common stock ranged from a low of $35.80 to a high of $63.41 per share, and the closing price of American Tower Class A common stock ranged from a low of $12.45 to a high of $19.00 per share. Lehman Brothers and Evercore noted the outperformance of SpectraSite common stock in the period reviewed relative to American Tower Class A common stock and the Standard & Poor’s 500 Index. Lehman Brothers and Evercore also noted the outperformance of American Tower Class A common stock in the period reviewed relative to the Standard & Poor’s 500 Index. The foregoing historical share price analysis was presented to the SpectraSite board of directors to provide it with background information and perspective with respect to the relative historical share prices of SpectraSite common stock and American Tower Class A common stock.

Historical Exchange Ratio Analysis. Lehman Brothers and Evercore also compared the historical per share closing prices of SpectraSite and American Tower during the period from April 30, 2004 to May 2, 2005, the last trading day prior to the delivery of Lehman Brothers’ and Evercore’s opinions, in order to determine the implied average exchange ratio that existed for those periods. The following table indicates the average exchange ratio of American Tower Class A common stock for SpectraSite common stock for the periods indicated:


		Average Exchange Ratio
May 2, 2005		3.235x
30-trading day period		3.258x
60-trading day period		3.292x
90-trading day period		3.252x
Six-month period		3.215x
One-year period		3.075x
52-week high		3.399x
52-week low		2.746x

The average exchange ratios above should be compared to the exchange ratio in the merger of 3.575x.

Comparable Companies Analysis. In order to assess how the public market values shares of similar publicly traded companies, Lehman Brothers and Evercore, based on their experience with companies in the wireless communications tower industry, reviewed and compared specific financial and operating data relating to SpectraSite and American Tower with the following companies that Lehman Brothers and Evercore deemed relevant to SpectraSite and American Tower:

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Crown Castle International Corporation

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Global Signal, Inc.

•

SBA Communications Corporation

As part of their comparable company analysis, Lehman Brothers and Evercore calculated and analyzed various financial multiples, including SpectraSite’s, American Tower’s and each comparable company’s enterprise value to certain projected 2005 financial metrics such as earnings before interest, taxes, depreciation and amortization, which Lehman Brothers refers to as EBITDA, and equity value to certain projected financial metrics such as levered free cash flow, defined as EBITDA less capital expenditures less interest expense less preferred dividends. The enterprise value of each company was obtained by adding its short and long term debt to the sum of the market value of its common equity, the value of any preferred stock, at liquidation value, and the book value of any minority interest, and subtracting its cash and cash equivalents. All of these calculations were performed, and based on publicly available financial data and closing prices, as of May 2, 2005, the last trading date prior to the delivery of Lehman Brothers’ and Evercore’s opinions.

The analysis of enterprise value as a multiple of projected 2005 EBITDA indicated that, for the selected comparable companies, the multiples of enterprise value as a multiple of projected 2005 EBITDA ranged from 15.5x to 17.5x. From this analysis, Lehman Brothers and Evercore derived implied exchange ratios ranging from 2.297x to 3.285x, compared to the exchange ratio in the merger of 3.575x.

The analysis of equity value as a multiple of projected 2005 levered free cash flow indicated that for the selected comparable companies, the multiples of equity value as a multiple of projected 2005 free cash flow ranged from 18.0x to 21.0x. From this analysis, Lehman Brothers and Evercore derived implied exchange ratios ranging from 2.494x to 3.394x, compared to the exchange ratio in the merger of 3.575x.

Lehman Brothers and Evercore selected the comparable companies listed above because their businesses and operating profiles are relevant to that of SpectraSite and American Tower. However, because of the inherent

differences between the businesses, operations and prospects of SpectraSite and American Tower and the businesses, operations and prospects of the selected comparable companies, no comparable company is exactly the same as SpectraSite or American Tower. Therefore, Lehman Brothers and Evercore believed that it was inappropriate to, and therefore did not, rely solely on the quantitative results of the comparable company analysis. Accordingly, Lehman Brothers and Evercore also made qualitative judgments concerning differences between the financial and operating characteristics and prospects of SpectraSite and American Tower and the companies included in the comparable company analysis that would affect the public trading values of each in order to provide a context in which to consider the results of the quantitative analysis. These qualitative judgments related primarily to the differing sizes, capital structure, growth prospects, profitability levels, degree of operational risk and recent and/or pending transactions between SpectraSite and American Tower and the companies included in the comparable company analysis.

Contribution Analysis. Lehman Brothers and Evercore analyzed the respective contributions of SpectraSite and American Tower to the EBITDA, EBITDA less capital expenditures and levered free cash flow of the combined company for the estimated calendar years 2005, 2006 and 2009 based on projections prepared by each company’s management. The Expected Synergies were not considered in this analysis. This analysis indicated the following relative contributions of SpectraSite and American Tower and the following implied exchange ratios:


Metric	2005E Contribution		2006E Contribution		2009E Contribution
EBITDA
SpectraSite	31	%	31	%	35	%
American Tower	69	%	69	%	65	%
Implied Exchange Ratio	2.790	x	2.830	x	3.434	x

EBITDA Less Capital Expenditures
SpectraSite	28	%	28	%	33	%
American Tower	72	%	72	%	67	%
Implied Exchange Ratio	2.235	x	2.173	x	3.101	x

Levered Free Cash Flow
SpectraSite	36	%	31	%	35	%
American Tower	64	%	69	%	65	%
Implied Exchange Ratio	2.909	x	2.341	x	2.766	x

This analysis indicated implied exchange ratios ranging from 2.173x to 3.434x, compared to the exchange ratio in the merger of 3.575x.

Research Analyst Price Targets. Lehman Brothers and Evercore compared selected recent publicly available research analyst price targets from selected firms who published price targets for both SpectraSite and American Tower as of May 2, 2005, the last trading day prior to the delivery of Lehman Brothers’ and Evercore’s opinions. In performing this analysis, Lehman Brothers and Evercore utilized research analyst price targets from the following firms:

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Bank of America Corp.

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Bear Stearns Companies, Inc.

•

Citigroup, Inc.

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Morgan Stanley

•

Raymond James Financial, Inc.

•

RBC Capital Markets Corp.

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Stanford Financial Group

For each firm, Lehman Brothers and Evercore calculated the exchange ratios based on the price targets for SpectraSite and American Tower, respectively. The analysis yielded exchange ratios ranging from 2.833x to 3.889x, compared to the exchange ratio in the merger of 3.575x.

Discounted Cash Flow Analysis. As part of their analyses, and in order to estimate the present value of SpectraSite common stock and American Tower Class A common stock, Lehman Brothers and Evercore prepared a five-year discounted cash flow analysis for SpectraSite and American Tower of after-tax unlevered free cash flows for fiscal years 2005 through 2009.

A discounted cash flow analysis is a valuation methodology used to derive a valuation of an asset by calculating the “present value” of estimated future cash flows of the asset. “Present value” refers to the current value of future cash flows or amounts and is obtained by discounting those future cash flows or amounts by a discount rate that takes into account macro-economic assumptions and estimates of risk, the opportunity cost of capital, expected returns and other appropriate factors. Lehman Brothers and Evercore performed a discounted cash flow analysis for SpectraSite and American Tower by adding (1) the present value of SpectraSite’s and American Tower’s projected after-tax unlevered free cash flows for fiscal years 2005 through 2009 to (2) the present values of the “terminal value” of SpectraSite and American Tower as of the end of 2009, respectively. “Terminal value” refers to the value of all future cash flows from an asset at a particular point in time.

Lehman Brothers and Evercore estimated, after taking into account selected comparable tower enterprise values to EBITDA multiples, a range of terminal values in 2009 calculated based on selected EBITDA multiples of 13.0x to 14.0x. Lehman Brothers and Evercore discounted the unlevered free cash flow streams and the estimated terminal value to a present value at a range of discount rates from 8.0% to 10.0%. The discount rates utilized in this analysis were chosen by Lehman Brothers and Evercore based on their expertise and experience with the wireless communications tower industry and also on an analysis of the weighted average cost of capital of SpectraSite, American Tower and other comparable companies. Lehman Brothers and Evercore calculated per share equity values by first determining a range of enterprise values of SpectraSite and American Tower by adding the present values of the after-tax unlevered free cash flows and terminal values for each EBITDA terminal multiple and discount rate scenario and then subtracting from the enterprise values the net debt, calculated as total debt minus cash, of SpectraSite and American Tower, respectively, and dividing those amounts by the number of fully diluted shares of SpectraSite and American Tower, respectively.

Based on the projections and assumptions set forth above, including the midpoint of the terminal value range, the discounted cash flow analysis implied exchange ratios ranging from 2.463x to 3.711x, compared to the exchange ratio in the merger of 3.575x.

Transaction Premium Analysis. Lehman Brothers and Evercore reviewed the premium paid in all publicly announced and consummated transactions involving 100% stock consideration valued at greater than $1.0 billion from January 1, 1995 to April 28, 2005 in which the pro forma ownership of the target companies’ stockholders ranged from 35% to 65%. Lehman Brothers and Evercore calculated the premium per share paid by the acquirer compared to the share price of the target company prevailing (1) one day, (2) one week and (3) four weeks prior to the announcement of the transaction. This analysis produced the following premiums and implied equity values for SpectraSite:


	Period Prior to Announcement
	Based on Median Premiums									Based on Mean Premiums
	One Day			One Week			One Month			One Day			One Week			One Month
SpectraSite share price	$	54.99		$	57.26		$	57.99		$	54.99		$	57.26		$	57.99
Median/mean premiums		5.9	%		5.5	%		7.1	%		10.3	%		11.8	%		11.8	%
Implied equity values per share of SpectraSite common stock	$	58.23		$	60.41		$	62.10		$	60.66		$	64.00		$	64.81
American Tower share price as of May 2, 2005	$	17.00		$	17.00		$	17.00		$	17.00		$	17.00		$	17.00
Implied Exchange Ratio		3.425	x		3.554	x		3.653	x		3.568	x		3.765	x		3.813	x

The analysis indicated implied exchange ratios ranging from 3.425x to 3.813x, compared to the exchange ratio in the merger of 3.575x.

Leveraged Acquisition Analysis. Lehman Brothers and Evercore performed a leveraged acquisition analysis on SpectraSite and American Tower in order to ascertain the prices that would be attractive to a potential financial buyer based upon current market conditions. Lehman Brothers and Evercore assumed the following in their analyses: (1) a capital structure comprised of 10x 2004 EBITDA of debt, or $1.965 billion and $4.345 billion for SpectraSite and American Tower, respectively, (2) an equity investment that would achieve a rate of return of approximately 18% to 25% and (3) a range of 13.0x to 14.0x EBITDA exit multiple in 2009.

Based on the projections and assumptions set forth above, the leveraged acquisition analysis yielded implied exchange ratios ranging from 2.656x to 4.330x, compared to the exchange ratio in the merger of 3.575x.

Pro Forma Analysis. In order to evaluate the estimated ongoing impact of the merger, Lehman Brothers and Evercore analyzed the effect of the merger on the free cash flow per share of both American Tower and SpectraSite. For the purposes of this analysis, Lehman Brothers and Evercore assumed (1) a $17.00 per share price for American Tower common stock as of May 2, 2005, (2) the Exchange Ratio of 3.575x implying a $60.78 per share price for SpectraSite common stock, (3) a transaction structure with 100% stock consideration, (4) the American Tower Projections and the SpectraSite Projections were accurate and having been adjusted for certain capital structure assumptions and (5) the Expected Synergies were accurate. Lehman Brothers and Evercore estimated that, based on the assumptions described above, the pro forma impact of the transaction on the levered free cash flow per share of American Tower would be 2% accretive in 2005 and 5% dilutive in 2006. Lehman Brothers and Evercore also estimated that, based on the assumptions described above, the pro forma impact of the transaction on the levered free cash flow per share of SpectraSite would be 26% accretive in 2005 and 35% accretive in 2006. The financial forecasts that underlie this analysis are subject to substantial uncertainty and, therefore, actual results may be substantially different.

Conflicts of Interests of SpectraSite Directors and Executive Officers in the Merger

When considering the recommendation of the SpectraSite board of directors to vote “FOR” the approval of the SpectraSite merger proposal, SpectraSite stockholders should be aware that some directors and executive officers of SpectraSite have agreements or arrangements that provide them with interests in the merger that are different from, or in addition to, the interests of SpectraSite stockholders. The board of directors of SpectraSite was aware of these interests and considered them, among other matters, during its deliberations with respect to the merger and in deciding to recommend that SpectraSite stockholders vote “FOR” the approval of the SpectraSite merger proposal.

Governance Structure. Pursuant to the terms of the merger agreement, upon consummation of the merger the American Tower board of directors will be composed of ten individuals, six of whom will be the current directors of American Tower and four of whom will be selected from the current SpectraSite board of directors. Assuming they are willing and able to serve, it is expected that two of the SpectraSite designees will be Stephen H. Clark and Timothy G. Biltz. The identity of the remaining two SpectraSite designees has not yet been determined.

The SpectraSite designees on the American Tower board of directors will be eligible to receive fees comparable to those received by non-employee directors on the American Tower board of directors. Because Messrs. Clark and Biltz are employees of SpectraSite, they have not received any fees for their duties on the SpectraSite board of directors.

SpectraSite Director Shares of Restricted Stock. In July 2005, each of Paul M. Albert, Jr., John F. Chlebowski, Dean J. Douglas, Patricia L. Higgins, Samme L. Thompson and Kari-Pekka Wilska will receive for nominal consideration an award of restricted shares of SpectraSite’s common stock in a number of shares equal in value to $60,000 at the time of the grant.

The form of Restricted Stock Award Agreement to be used in connection with this July 2005 grant provides that these restricted shares of SpectraSite’s common stock shall become fully vested upon a Transfer of Control, as defined in the Restricted Stock Award Agreement. The consummation of the merger will constitute a Transfer of Control, resulting in the full vesting of these awards. Thus, each of these formerly restricted shares of SpectraSite’s common stock shall be treated the same as all other shares of SpectraSite common stock, with the result that, upon consummation of the merger, they will be converted into the right to receive 3.575 shares of American Tower Class A common stock.

SpectraSite Director and Employee Stock Options. Upon consummation of the merger, each outstanding option to purchase shares of SpectraSite common stock, whether vested or unvested, will be assumed by American Tower. Each SpectraSite stock option assumed by American Tower will be exercisable upon the same terms and conditions as under the SpectraSite stock option plans and the applicable SpectraSite stock option agreements, except that such option to purchase SpectraSite common stock will be exercisable for that whole number of shares of American Tower Class A common stock rounded down to the nearest whole share equal to the aggregate number of shares of SpectraSite common stock subject to such SpectraSite stock option multiplied by 3.575 and will be exercisable at an exercise price equal to the current exercise price of such SpectraSite stock option divided by 3.575 rounded upward to the nearest full cent.

In addition, the consummation of the merger may in certain circumstances cause accelerated vesting of unvested options with performance based vesting schedules, which we refer to as performance options and options with time based vesting schedules, which we refer to as service options, as follows:

Performance Options. Unless the SpectraSite board of directors determines that certain performance targets for 2005 will be missed by 15% or more and assuming the merger occurs before these performance options would otherwise vest, the unvested performance options will become vested upon consummation of the merger.

Service Options. Under the terms of SpectraSite’s employment agreements with each of Messrs. Clark, Biltz and Slaven, if any of these individuals is terminated without Cause or resigns with Good Reason, each as defined in the executive officer’s employment agreement, before or after the consummation of the merger, any remaining unvested portion of his service option will become fully vested. Pursuant to the terms of the merger agreement, if any other officer of SpectraSite is terminated without Cause or resigns with Good Reason, each as defined in SpectraSite’s 2003 Equity Incentive Plan, in the year following the consummation of the merger, any remaining unvested portion of his or her service option will become fully vested. Additionally, prior to the merger SpectraSite intends to amend an option agreement of Mr. Albert, a director of SpectraSite, to provide that the unvested portion of Mr. Albert’s options subject to the option agreement will become vested immediately upon consummation of the merger.

Severance. Under the terms of SpectraSite’s employment agreements with each of Messrs. Clark, Biltz and Slaven or under the terms of SpectraSite’s Executive Severance Plan B in the case of SpectraSite’s other executive officers, executive officers of SpectraSite may be entitled to enhanced severance payments and benefits as a result of the consummation of the merger if their employment ceases under certain specified circumstances in anticipation of or within two years following the consummation of the merger. As Messrs. Clark, Biltz and Slaven will not continue as employees of American Tower after consummation of the merger, each will be entitled to such benefits as set forth in the table below. In addition, if any amount paid to Mr. Slaven under this or any other arrangement is considered an “excess parachute payment” under the federal tax laws, then Mr. Slaven will be entitled to an additional “gross-up” payment, of up to $2.056 million, for any resulting additional excise taxes.

The following table sets forth for SpectraSite’s directors and executive officers the number of additional shares of SpectraSite common stock with respect to which options, including performance options and service options, may become vested and potential severance payments and benefits described above. The information with respect to option vesting and potential severance payments assumes that the SpectraSite board of directors does not determine that certain performance targets will be missed by 15% or more, that the merger will be consummated on September 30, 2005, that Messrs. Clark, Biltz and Slaven will be terminated on that same date without Cause and that all of the other executive officers will be terminated on December 30, 2005 without Cause. The assumption that the merger will be consummated on September 30, 2005 is for illustrative purposes only. The merger may be consummated before or after September 30, 2005, which could result in the amounts set forth below being higher or lower.


	Accelerated Vesting of Options
Name	Number of Shares Acquired on Exercise	Weighted Average Exercise Price		Accelerated Vesting of Restricted Shares(1)		Potential Severance Payments and Cash Benefits(2)
Stephen H. Clark	280,094	$	14.9100	$	—	$	2,431,733
Timothy G. Biltz	178,240		13.0750		—		1,946,356
Paul M. Albert, Jr.	1,333		13.0750		60,000		—
John F. Chlebowski	—		—		60,000		—
Dean J. Douglas	—		—		60,000		—
Patricia L. Higgins	—		—		60,000		—
Samme L. Thompson	—		—		60,000		—
Kari-Pekka Wilska	—		—		60,000		—
Dale A. Carey	44,860		13.0750		—		792,032
Gabriela Gonzalez	12,591		13.0750		—		613,591
John H. Lynch	12,591		13.0750		—		623,050
Thomas A. Prestwood, Jr.	21,250		13.0750		—		662,480
Mark A. Slaven	162,499		56.5325		—		1,666,851	(3)

(1)	Represents dollar value of restricted shares to be granted and assumes that there is no increase in value between date of grant and consummation of the merger.

(2)	Includes amounts related to estimated pro rata bonuses to be paid upon consummation of the merger.

(3)	In addition, if any amount paid to Mr. Slaven is considered an “excess parachute payment” under the federal tax laws, then Mr. Slaven will be entitled to an additional “gross up” payment, of up to $2.056 million, for any resulting additional excise taxes.

Indemnification and Insurance. The merger agreement provides that all rights to indemnification by SpectraSite existing in favor of each present and former director and officer of SpectraSite or its subsidiaries in effect on date of the merger agreement as provided for in SpectraSite’s certificate of incorporation or by-laws or pursuant to any other agreements will survive the merger. Additionally, the merger agreement also provides that American Tower will maintain, for a period of at least six years from the effective time of the merger, and perform, in a timely manner, its obligations with respect to the foregoing indemnification obligations in favor of each present and former director and officer of SpectraSite or its subsidiaries. In addition, American Tower has agreed to maintain in effect for a period of six years from and after the consummation of the merger the current directors’ and officers’ liability insurance policies of SpectraSite containing coverage at the same level maintained at or prior to the consummation of the merger. American Tower, however, will not be required to expend more than an amount per year equal to 200% of current annual premiums paid by SpectraSite for such insurance. If American Tower would be required to expend more than 200% of current annual premiums, it will obtain the maximum amount of such insurance obtainable by payment of annual premiums equal to 200% of current annual premiums.

Consummation and Effectiveness of the Merger

American Tower and SpectraSite are working toward consummating the merger as quickly as possible. American Tower and SpectraSite intend to consummate the merger when all of the conditions to consummation of the merger are satisfied or waived in accordance with the merger agreement. American Tower and SpectraSite expect to consummate the merger by the end of the second half of 2005.

Conversion of SpectraSite Common Stock

For a description of the consideration to be received in the merger by holders of SpectraSite common stock, see the section captioned “THE MERGER AGREEMENT—Consideration to be Received in the Merger” beginning on page 73.

American Tower Class A common stock outstanding immediately prior to the merger will remain outstanding and unaffected by the merger.

Treatment of SpectraSite Stock Options

All outstanding SpectraSite stock options, whether or not exercisable and whether or not vested, will remain outstanding following the effective time of the merger, and American Tower will assume these SpectraSite stock options as described below.

Each SpectraSite stock option assumed by American Tower shall be exercisable upon the same terms and conditions as under the SpectraSite stock option plans and the applicable SpectraSite stock option agreements,

except that such option to purchase SpectraSite common stock will be exercisable for that whole number of shares of American Tower Class A common stock rounded down to the nearest whole share equal to the aggregate number of shares of SpectraSite common stock subject to such SpectraSite stock option multiplied by 3.575 and will be exercisable at an exercise price equal to the current exercise price of such SpectraSite stock option divided by 3.575 rounded upward to the nearest full cent. The consummation of merger will result in the vesting of unvested SpectraSite stock options on the same terms and conditions as were applicable under, and only to the extent expressly provided for by the terms of, the SpectraSite stock option plans, but taking into account any changes provided for in the SpectraSite stock options plans or in the SpectraSite stock options by reason of merger.

If the merger occurs before the performance options would otherwise vest, under the terms of the applicable award agreements pursuant to which SpectraSite stock options have been granted, immediately prior to the effective time of the merger, the SpectraSite board of directors will determine whether the unvested SpectraSite performance options will become vested. This determination will be made in accordance with the terms of the applicable award agreements and the SpectraSite 2003 Equity Incentive Plan and will be based on whether SpectraSite meets certain operating performance requirements for the period prior to the effective time of the merger.

American Tower and SpectraSite also agreed that SpectraSite service options will vest if the employment of the holder of these service options is either terminated without Cause (as defined in the SpectraSite 2003 Equity Incentive Plan) or terminates as a result of the holder’s resignation for Good Reason (as defined in the SpectraSite 2003 Equity Incentive Plan) at any time after the effective time of the merger but before the one year anniversary of the effective time of the merger.

Additionally, prior to the merger SpectraSite intends to amend an option agreement of Mr. Albert, a director of SpectraSite, to provide that the unvested portion of Mr. Albert’s options subject to the option agreement will become vested immediately upon consummation of the merger.

Under the terms of SpectraSite’s employment agreements with each of Messrs. Clark, Biltz and Slaven, if any of these individuals is terminated without Cause or resigns with Good Reason, each as defined in the executive officer’s employment agreement, before or after the consummation of the merger, any remaining unvested portion of his service option will become fully vested.

As soon as practicable after the effective time of the merger, American Tower shall deliver to each holder of SpectraSite stock options an appropriate notice setting forth such holder’s rights.

Treatment of SpectraSite’s Warrants

As of the effective time of the merger, the outstanding SpectraSite warrants to purchase shares of SpectraSite common stock will, in accordance with and subject to the applicable provisions of the SpectraSite warrants, remain outstanding after the effective time of the merger and be exercisable in accordance with the terms of the SpectraSite warrants, except that each SpectraSite warrant will be exercisable for that number of shares of American Tower Class A common stock equal to the aggregate shares of SpectraSite common stock subject to such SpectraSite warrant multiplied by 3.575 and will be exercisable at an exercise price equal to the current exercise price of such SpectraSite warrant divided by 3.575.

Treatment of SpectraSite’s Restricted Stock

Each outstanding share of SpectraSite common stock that is subject to a repurchase option or risk of forfeiture will be exchanged for 3.575 shares of American Tower Class A common stock and will be fully vested and will cease to be subject to any such restrictions as of the effective time of the merger.

Board of Directors, Officers and Governing Documents of American Tower after the Merger

If the merger is consummated, American Tower has agreed to expand the size of its board of directors from six directors to ten directors. All six current members of the American Tower board of directors will continue to serve as directors of American Tower following the merger. Effective as of the consummation of the merger, American Tower will appoint to the American Tower board of directors Messrs. Clark and Biltz and two other directors from the SpectraSite board of directors, who will be designated by SpectraSite and must be reasonably acceptable to American Tower. If either or both of Messrs. Clark and Biltz are unwilling or unable to serve as a director of American Tower as of the consummation of the merger, then SpectraSite will designate another individual or individuals, as the case may be, from the board of directors of SpectraSite, who must be reasonably acceptable to American Tower, to serve on the American Tower board of directors. The terms of all members of the American Tower board of directors, including the SpectraSite directors appointed in connection with the merger, will expire at the next annual meeting of the American Tower stockholders, which will occur in 2006. See the section captioned “THE MERGER AGREEMENT—Board of Directors of the Combined Company” beginning on page 88.

The current executive officers of American Tower will remain executive officers of American Tower following the merger, including Messrs. Taiclet and Singer, as the Chief Executive Officer and Chief Financial Officer, respectively.

As a result of the merger, each share of SpectraSite common stock will be converted automatically into the right to receive 3.575 shares of American Tower Class A common stock. Accordingly, the principal documents governing your rights as stockholders of American Tower will be those set forth in the American Tower certificate of incorporation and by-laws. A summary of important terms of American Tower’s capital stock is set forth in the section captioned “AMERICAN TOWER DESCRIPTION OF CAPITAL STOCK” beginning on page 90 and a comparison of the rights of American Tower and SpectraSite stockholders is set forth in the section captioned “COMPARISON OF RIGHTS OF AMERICAN TOWER STOCKHOLDERS AND SPECTRASITE STOCKHOLDERS” beginning on page 100. In addition to the American Tower merger proposal, American Tower is seeking stockholder approval of a proposal to amend and restate its certificate of incorporation, as more fully described in the section captioned “AMERICAN TOWER STOCKHOLDERS ONLY— AMERICAN TOWER PROPOSAL NUMBER TWO: TO AMEND AND RESTATE THE AMERICAN TOWER CORPORATION RESTATED CERTIFICATE OF INCORPORATION” beginning on page 103. If this proposal is approved by the American Tower stockholders, the Amended and Restated Certificate of Incorporation attached as Annex E to this joint proxy statement/prospectus will govern your rights as stockholders of American Tower after the merger.

Regulatory Matters

Antitrust Considerations. Under U.S. antitrust laws, transactions such as the merger typically may not be consummated until the parties have notified the Antitrust Division and the FTC of the transaction and have made any necessary filings under and satisfied the waiting period requirements of the HSR Act. The HSR Act and related regulations contain certain exceptions to the obligation to satisfy the notification and waiting period requirements. Based upon communications among American Tower, SpectraSite and the Premerger Notification Office of the FTC, the parties have concluded that consummation of the merger is not subject to the notification and waiting period requirements of the HSR Act and, therefore, no filing under the HSR Act will be made.

The Antitrust Division has informed American Tower and SpectraSite that it is investigating the merger and requested information and materials from American Tower and SpectraSite with respect to the merger. American Tower and SpectraSite are cooperating with the Antitrust Division to provide the information and materials that have been requested to date. The Antitrust Division may request additional information or other materials with respect to the merger. In addition, the Antitrust Division may challenge the merger on antitrust grounds as it deems necessary or desirable in the public interest, including seeking to enjoin the merger or seeking to cause

divestitures of significant assets of American Tower or SpectraSite or their respective subsidiaries. In addition, American Tower and SpectraSite may agree in connection with the Antitrust Division’s investigation of the merger to a divestiture of certain assets or to agree to other restrictions on the conduct of its business to avoid or settle such a challenge by the Antitrust Division.

Additionally, at any time before or after the consummation of the merger, any state or foreign governmental entity could take action under the antitrust laws as it deems necessary or desirable in the public interest, or other persons can take action under the antitrust laws. There is no assurance that a challenge to the merger will not be made or that, if a challenge is made, American Tower and SpectraSite will prevail.

Accounting Treatment of the Merger

American Tower intends to account for the merger under the purchase method of accounting for business combinations.

Restrictions on Sales of Shares by Affiliates of SpectraSite

The shares of American Tower Class A common stock to be issued in connection with the merger will be registered under the Securities Act and will be transferable under the Securities Act, except for shares of American Tower Class A common stock issued to any person who is deemed to be an “affiliate” of SpectraSite at the time of the SpectraSite special meeting. Persons who may be deemed to be affiliates include individuals or entities that control, are controlled by, or are under the common control of SpectraSite and may include executive officers, directors and major stockholders of SpectraSite. Affiliates may not sell their shares of American Tower Class A common stock acquired in connection with the merger except pursuant to:

•

an effective registration statement under the Securities Act covering the resale of those shares;

•

an exemption under paragraph (d) of Rule 145 under the Securities Act; or

•

any other applicable exemption under the Securities Act.

American Tower’s registration statement on Form S-4, of which this joint proxy statement/prospectus forms a part, does not cover the resale of shares of American Tower Class A common stock to be received by SpectraSite’s affiliates in connection with the merger.

Appraisal Rights

Under Delaware law, no SpectraSite stockholder is entitled to appraisal rights in connection with the merger.

Delisting and Deregistration of SpectraSite Common Stock after the Merger

If the merger is consummated, SpectraSite common stock will be delisted from the NYSE and will be deregistered under the Exchange Act.

MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS OF THE MERGER

The following discussion describes the material U.S. federal income tax considerations applicable to SpectraSite stockholders of the exchange of SpectraSite common stock for American Tower Class A common stock pursuant to the merger as of the date hereof.

For purposes of this discussion, a “U.S. holder” means a beneficial owner of SpectraSite common stock that is any of the following for U.S. federal income tax purposes: (1) a citizen or resident of the United States, (2) a corporation created or organized in or under the laws of the United States, any state thereof, or the District of Columbia, (3) an estate the income of which is subject to U.S. federal income taxation regardless of its source, or (4) a trust if (a) its administration is subject to the primary supervision of a court within the United States and one or more U.S. persons have the authority to control all of its substantial decisions, or (b) it has a valid election in effect under applicable U.S. Treasury regulations to be treated as a U.S. person. A “non-U.S. holder” means a beneficial owner of SpectraSite common stock, other than an entity classified as a partnership for U.S. federal income tax purposes, that is not a U.S. holder.

This discussion is based upon provisions of the Internal Revenue Code, and regulations, rulings and judicial decisions as of the date hereof. Those authorities may be changed, perhaps retroactively, or be subject to differing interpretations, so as to result in U.S. federal tax considerations different from those summarized below. This discussion does not represent a detailed description of the U.S. federal tax considerations to SpectraSite stockholders in light of their particular circumstances or to stockholders that are subject to special treatment under the U.S. federal tax laws, such as dealers in securities or currencies, traders in securities that use a mark-to-market method of accounting for securities holdings, financial institutions, tax-exempt entities, insurance companies, persons holding common stock as part of a hedging, integrated, conversion or constructive sale transaction or a straddle, individuals who received their SpectraSite common stock upon the exercise of employee stock options or otherwise as compensation, U.S. persons whose functional currency is not the U.S. dollar, U.S. expatriates, “controlled foreign corporations,” “passive foreign investment companies” or investors in pass-through entities, and it does not address any taxes other than the U.S. federal income tax. This discussion also does not address considerations under the alternative minimum tax. This discussion is limited to persons who hold SpectraSite common stock, and will hold American Tower Class A common stock, as capital assets. Except where specifically provided below, this discussion does not describe considerations applicable to a non-U.S. holder of SpectraSite common stock who (1) holds or held, at any time during the shorter of (a) the five-year period preceding the date of the merger or (b) the holder’s holding period, more than five percent of the shares of SpectraSite common stock, (2) is engaged in a trade or business within the United States, (3) in the case of certain individual non-U.S. holders, is present in the United States for 183 days or more in the taxable year of the merger or (4) is affected by the provisions of an income tax treaty to which the United States is a party.

If an entity classified as a partnership for U.S. federal income tax purposes holds SpectraSite common stock, the tax treatment of a partner will generally depend on the status of the partner and the activities of the partnership. Any stockholder that is a partnership holding SpectraSite common stock, or any partner in such a partnership, should consult its tax advisors.

SpectraSite stockholders are strongly urged to consult their tax advisors as to the specific tax considerations of the merger, including the applicability and effect of federal, state, local and foreign income and other tax laws in their particular circumstances.

General

In connection with the mailing of this joint proxy statement/prospectus, American Tower and SpectraSite will receive legal opinions from King & Spalding LLP and Paul, Weiss, Rifkind, Wharton & Garrison LLP, respectively, to the effect that

•

the merger will be treated for U.S. federal income tax purposes as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code; and

•

American Tower and SpectraSite will each be a party to that reorganization within the meaning of Section 368(b) of the Internal Revenue Code.

These opinions were rendered on the basis of customary representations and covenants, including representations and covenants regarding the absence of changes in existing facts and including representations contained in officers’ certificates of American Tower and SpectraSite, and of customary assumptions, including that the merger will be consummated in accordance with this joint proxy statement/prospectus and the merger agreement and that the representations made by each of American Tower and SpectraSite are true and accurate in all respects and will remain true and accurate in all respects at all times up to and including the effective time of the merger. If any of those representations are inaccurate, incomplete or untrue or any of the covenants are breached, the conclusions contained in the opinions referred to in this paragraph could be affected. Neither American Tower nor SpectraSite is currently aware of any facts or circumstances that would cause any representations made by it to King & Spalding LLP or Paul, Weiss, Rifkind, Wharton & Garrison LLP to be untrue or incorrect in any material respect. None of the opinions referred to in this paragraph will be binding on the Internal Revenue Service or the courts, and no rulings will be sought from the Internal Revenue Service regarding the tax treatment of the merger. Accordingly, there can be no assurance that the Internal Revenue Service will not challenge the conclusions set forth in any of the opinions stated herein or that a court would not sustain such a challenge.

Based on the above, the following additional income tax consequences would arise:

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Gain or loss. No gain or loss will be recognized by SpectraSite stockholders as a result of the merger, except with respect to any cash received in the merger.

•

Tax basis. The aggregate tax basis of the shares of American Tower Class A common stock received by a SpectraSite stockholder in the merger will be the same as the aggregate basis of SpectraSite common stock for which it is exchanged, less any basis attributable to fractional shares of American Tower Class A common stock for which cash is received.

•

Holding period. The holding period of the shares of American Tower Class A common stock received by a SpectraSite stockholder in the merger will include the holding period of the stockholder’s SpectraSite common stock surrendered in exchange for American Tower Class A common stock.

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Fractional shares. A SpectraSite stockholder who receives cash in lieu of fractional shares of American Tower Class A common stock will be treated as having received the fractional shares in the merger and then having exchanged the fractional shares for cash in a redemption by American Tower. As a result, such stockholder will generally recognize gain or loss equal to the difference between the amount of cash received and the stockholder’s tax basis in the fractional share interest. Any gain or loss attributable to fractional shares generally will be capital gain or loss, and will be long-term capital gain or loss if, as of the effective date of the merger, the holding period for such shares is greater than one year. Long-term capital gain of a non-corporate U.S. holder is eligible to be taxed at reduced rates. The deductibility of capital losses is subject to limitations. Subject to the discussion below, a non-U.S. holder will generally not be subject to U. S. federal income tax with respect to such gain, unless (1) such gain is effectively connected with the conduct of a trade or business within the United States by the non-U.S. holder or (2) such non-U.S. holder is an individual who is present in the United States for 183 days or more in the taxable year of the merger and certain other conditions are met.

Certain Additional Tax Considerations of the Merger to Non-U.S. Holders

Certain provisions of the Internal Revenue Code, enacted pursuant to United States tax legislation referred to as the Foreign Investment in Real Property Tax Act, which we refer to as FIRPTA, generally subject any gain or loss realized by a foreign person in connection with the sale or exchange of a “United States real property interest,” which we refer to as a USRPI, to U.S. federal income tax as either ordinary income or capital gain that is effectively connected with the foreign person’s conduct of a trade or business in the United States, which we refer to as the FIRPTA Tax.

For purposes of the FIRPTA Tax, stock held in a “United States real property holding corporation,” which we refer to as a USRPHC, generally is classified as a USRPI. A corporation generally is classified as a USRPHC if the fair market value of its interests in United States real property equals or exceeds 50% of the sum of the fair market value of its worldwide real property interests plus any other assets used or held for use in its trade or business. However, a foreign stockholder’s interest in a USRPHC will not be treated as a USRPI if (1) the relevant class of stock of the USRPHC is “regularly traded on an established securities market” under applicable Internal Revenue Code provisions and (2) that foreign stockholder has not held, either directly or indirectly, after taking into account applicable constructive ownership rules, including rules that treat a foreign stockholder as owning shares that are (1) owned by, or that are subject to an option held by, certain family members, corporations, partnerships, estates or trusts or (2) subject to an option held by that foreign stockholder, more than 5% of the outstanding shares of such relevant class of stock of the USRPHC at any time during the shorter of (1) the five-year period ending on the date of the disposition of such interest or (2) the period during which such stockholder held such interest.

Each of American Tower and SpectraSite believes that it is currently a USRPHC. American Tower and SpectraSite also each expect that their common stock will continue to be regularly traded on the NYSE leading up to and as of the effective time of the merger, such that American Tower and SpectraSite common stock should be considered to be “regularly traded on an established securities market” for purposes of the Internal Revenue Code.

If these expectations prove to be correct, so long as such non-U.S. holder of SpectraSite common stock holds or held, at all times, during the shorter of (1) the five-year period preceding the date of the merger or (2) the holder’s holding period, five percent or less of SpectraSite common stock, such holder will not recognize gain or loss as a result of the merger. Non-U.S. holders who hold or held, at any time during the shorter of (1) the five-year period preceding the date of the merger or (2) the holder’s holding period, more than five percent of SpectraSite common stock and who will own five percent or less of American Tower Class A common stock immediately following the merger may recognize gain as a result of the merger and should consult their tax advisors as to the tax consequences to them of the merger. Subject to the discussion of reporting requirements described below, other non-U.S. holders who hold or held, at any time during the shorter of (1) the five-year period preceding the date of the merger or (2) the holder’s holding period, more than five percent of SpectraSite common stock and who will own more than five percent of American Tower Class A common stock immediately following the merger will not recognize gain as a result of the merger and should consult their tax advisors as to the tax consequences to them of the merger.

Tax Opinions as Condition to Merger

Consummation of the merger is conditioned upon, among other things, the receipt by American Tower of a further opinion of King & Spalding LLP and the receipt by SpectraSite of a further opinion of Paul, Weiss, Rifkind, Wharton & Garrison LLP, on the closing date of the merger, to the effect that the merger will be treated for U.S. federal income tax purposes as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code and that American Tower and SpectraSite will each be a party to that reorganization within the meaning of Section 368(b) of the Internal Revenue Code. In rendering their opinions, counsel will require and rely upon customary representations and covenants. Neither American Tower nor SpectraSite is currently aware

of any facts or circumstances that would cause any representations made by it to King & Spalding LLP or Paul, Weiss, Rifkind, Wharton & Garrison LLP in connection with these further opinions to be untrue or incorrect in any material respect.

Reporting Requirements

U.S. holders of SpectraSite common stock receiving American Tower Class A common stock in the merger must file a statement with their U.S. federal income tax returns setting forth their tax basis in the SpectraSite common stock exchanged in the merger and the fair market value of the American Tower Class A common stock and the amount of any cash received in the merger. A non-U.S. holder of SpectraSite common stock who holds or held, at any time during the shorter of (1) the five-year period preceding the date of the merger or (2) the holder’s holding period, more than five percent of SpectraSite common stock must file an income tax return for the year of the merger and must attach a disclosure schedule (as provided in applicable U.S. Treasury regulations). In addition, SpectraSite stockholders will be required to retain permanent records of these facts relating to the merger.

Information Reporting and Backup Withholding

Payments of cash in lieu of fractional shares of American Tower Class A common stock may, under certain circumstances, be subject to information reporting and backup withholding unless the recipient provides proof of an applicable exemption or furnishes its taxpayer identification number, and otherwise complies with all applicable requirements of the backup withholding rules. Any amounts withheld from payments to a SpectraSite stockholder under the backup withholding rules are not additional tax and will be allowed as a credit against the stockholder’s U.S. federal income tax liability, provided the required information is timely furnished to the Internal Revenue Service.

THE MERGER AGREEMENT

The following is a summary of selected provisions of the merger agreement. While American Tower and SpectraSite believe this description addresses the material terms of the merger agreement, this summary may not contain all of the information that is important to you and is qualified in its entirety by reference to the merger agreement, which is attached as Annex A to this joint proxy statement/prospectus and is incorporated by reference herein. The rights and obligations of the parties are governed by the express terms and conditions of the merger agreement and not by this summary or any other information contained in this joint proxy statement/prospectus. American Tower stockholders and SpectraSite stockholders are urged to read the merger agreement carefully and in its entirety as well as this joint proxy statement/prospectus before making any decisions regarding the merger.

The representations, warranties and covenants contained in the merger agreement were made only for purposes of such agreement and as of specific dates, were solely for the benefit of the parties to such agreement, and may be subject to limitations agreed by the contracting parties, including being qualified by disclosures exchanged between the parties in connection with the execution of the merger agreement. The representations and warranties may have been made for the purposes of allocating contractual risk between the parties to the agreement instead of establishing these matters as facts, and may be subject to standards of materiality applicable to the contracting parties that differ from those applicable to investors. Investors are not third-party beneficiaries under the merger agreement and should not rely on the representations, warranties and covenants or any descriptions thereof as characterizations of the actual state of facts or condition of American Tower or SpectraSite or any of their respective subsidiaries.

Form of Merger

Upon the terms and subject to the conditions of the merger agreement and in accordance with Delaware law, at the effective time of the merger, SpectraSite will be merged with and into Asteroid Merger Sub, a Delaware limited liability company and a direct wholly owned subsidiary of American Tower formed solely for the purpose of engaging in the merger. As a result of the merger, the separate corporate existence of SpectraSite will cease and Asteroid Merger Sub will survive and continue as a direct wholly owned subsidiary of American Tower.

At the option of American Tower, the structure of the merger may be changed to consist of a merger of Asteroid Merger Sub with and into SpectraSite in which SpectraSite will survive and continue as a direct wholly owned subsidiary of American Tower. American Tower and SpectraSite will work in good faith to agree on appropriate amendments to the representations, warranties, covenants and other agreements in the merger agreement to give effect to the foregoing change in the structure of the merger. However, if the parties cannot agree on such amendment or the respective tax counsel to each party cannot deliver its opinion to the effect that (1) the merger will be treated for federal income tax purposes as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code and (2) that SpectraSite and American Tower will each be a party to that reorganization within the meaning of Section 368(b) of the Internal Revenue Code, then the merger will not be restructured. See the section captioned “—Conditions to Consummation of the Merger” beginning on page 75.

Consummation and Effectiveness of the Merger

Consideration to be Received in the Merger

For each share of SpectraSite common stock, SpectraSite stockholders will have the right to receive 3.575 shares of American Tower Class A common stock. Upon consummation of the merger, each share of SpectraSite common stock, other than shares held in treasury and shares owned directly by American Tower, issued and

outstanding immediately prior to the consummation of the merger will automatically be cancelled and converted into the right to receive 3.575 shares of American Tower Class A common stock.

SpectraSite stockholders will receive cash for any fractional shares that they would otherwise receive in the merger. The amount of cash, without interest, for fractional shares SpectraSite stockholders will receive will be calculated by multiplying the fractional share interest to which each such stockholder would be entitled by the average of the per share closing prices of shares of American Tower Class A common stock as reported on the NYSE during the ten consecutive trading days ending on and including the trading day immediately prior to the date of the effective time of the merger.

Based upon the outstanding number of shares of American Tower Class A common stock and SpectraSite common stock as of May 20, 2005, immediately after the merger, American Tower stockholders will own approximately 58% of the combined company and former SpectraSite stockholders will own approximately 42% of the combined company.

See the section captioned “PROPOSAL NUMBER ONE: THE MERGER PROPOSALS—Treatment of SpectraSite Stock Options” beginning on page 65, “PROPOSAL NUMBER ONE: THE MERGER PROPOSALS—Treatment of SpectraSite’s Warrants” beginning on page 66 and “PROPOSAL NUMBER ONE: THE MERGER PROPOSALS—Treatment of SpectraSite’s Restricted Stock” beginning on page 66.

Procedures for Exchange of Certificates

As promptly as practicable after consummation of the merger, American Tower’s exchange agent will mail to former SpectraSite stockholders a letter of transmittal and instructions to be used in surrendering certificates that represented shares of SpectraSite common stock prior to the consummation of the merger. When a former SpectraSite stockholder delivers these certificates to the exchange agent together with a properly executed letter of transmittal and any other required documents, the former SpectraSite stockholder will be entitled to receive American Tower stock certificates representing the number of whole shares of American Tower Class A common stock to which the stockholder is entitled under the merger agreement, cash in lieu of any fractional shares of American Tower Class A common stock to which such stockholder would be entitled and any dividends or distributions to which such stockholder is entitled.

In the event of a transfer of ownership of SpectraSite common stock that is not registered in SpectraSite’s transfer records, if a transferee presents the certificate representing such transferred shares to the exchange agent, accompanied by all documents required to evidence and effect such transfer and by evidence that any applicable stock transfer taxes have been paid, then such transferee will receive a certificate representing the proper number of shares of American Tower Class A common stock which such transferee has the right to receive in respect of such transferee’s shares of SpectraSite common stock formerly represented by such certificate, cash in lieu of any fractional shares of American Tower Class A common stock to which such holder is entitled pursuant the merger agreement and any dividends or other distributions to which such holder is entitled pursuant to the merger agreement.

No dividends or other distributions declared or made after the consummation of the merger with respect to American Tower Class A common stock with a record date after the consummation of the merger will be paid to the holder of any unsurrendered certificate formerly representing shares of SpectraSite common stock with respect to the shares of American Tower Class A common stock represented thereby until the holder of such certificate surrenders such certificate. Subject to the effect of applicable law, following surrender of any certificates, the holder of the certificates representing shares of American Tower Class A common stock issued in exchange therefore will be paid, without interest:

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promptly, the amount of dividends or other distributions with a record date after the consummation of the merger and theretofore paid with respect to such shares of American Tower Class A common stock; and

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at the appropriate payment date, the amount of dividends or other distributions, with a record date after the consummation of the merger but prior to surrender and a payment date occurring after surrender, payable with respect to such shares of American Tower Class A common stock.

Conditions to Consummation of the Merger

Each of American Tower and SpectraSite is required to consummate the merger only if specific conditions are satisfied or waived, including the following:

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the approval and adoption of the merger agreement, including the merger and the other transactions contemplated thereby, by holders of at least a majority of the outstanding shares of SpectraSite common stock;

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the approval of the issuance of American Tower Class A common stock in connection with the merger by the affirmative vote of holders of at least a majority of all shares of American Tower Class A common stock casting votes at the American Tower special meeting, provided that the total votes cast represents over 50% in interest of all securities entitled to vote;

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the absence of any applicable law or any restraining order, injunction or other judgment issued by any court or other government entity of competent jurisdiction prohibiting consummation of the merger;

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the effectiveness of, and the absence of any stop order or proceeding seeking a stop order with respect to, the registration statement on Form S-4 of which this joint proxy statement/prospectus forms a part; and

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the approval for listing on the NYSE, subject to official notice of issuance, of the shares of American Tower Class A common stock issuable to SpectraSite stockholders in connection with the merger.

The obligations of American Tower to effect the merger are subject to satisfaction or waiver at or prior to the closing of the merger of, among other things, the following additional conditions:

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the representations and warranties of SpectraSite with respect to (1) its organization and good standing, (2) its capitalization, (3) its authority to enter into and perform the obligations under the merger agreement and (4) the merger not conflicting with its organizational documents being true and correct in all material respects both as of the date of the merger agreement and as of closing of the merger, except for representations or warranties expressly made as of a specific date, the accuracy of which will be determined as of the specified date;

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all other representations and warranties of SpectraSite being true and correct, but without regard to materiality qualifications or references to a material adverse effect that may be contained in any representation or warranty, both as of the date of the merger agreement and as of the date of the closing of the merger, except for representations or warranties expressly made as of a specific date, the accuracy of which will be determined as of the specified date, except where any failure of such representations and warranties to be true and correct does not have and would not reasonably be expected to have, individually or in the aggregate, a material adverse effect on SpectraSite;

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SpectraSite having performed in all material respects all obligations required to be performed by it under the merger agreement at or prior to the consummation of the merger;

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SpectraSite having delivered to American Tower a certificate to the effect that each of the conditions specified above has been satisfied in all respects; and

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American Tower having received from King & Spalding LLP, counsel to American Tower, on the closing date of the merger, an opinion stating that the merger will be treated for U.S. federal income tax purposes as a “reorganization” within the meaning of Section 368(a) of the Internal Revenue Code and that SpectraSite and American Tower will each be a party to that reorganization within the meaning of Section 368(b) of the Internal Revenue Code.

The obligations of SpectraSite to effect the merger are subject to satisfaction or waiver at or prior to the closing of the merger of, among other things, the following additional conditions:

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the representations and warranties of American Tower and Asteroid Merger Sub with respect to (1) their organization and good standing, (2) their capitalization, (3) their authority to enter into the transaction and (4) the transaction not conflicting with their organizational documents being true and correct in all material respects both as of the date of the merger agreement and as of closing of the merger, except for representations or warranties expressly made as of a specific date, the accuracy of which will be determined as of the specified date;

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all other representations and warranties of American Tower and Asteroid Merger Sub being true and correct, but without regard to materiality qualifications or references to a material adverse effect that may be contained in any representation or warranty both as of the date of the merger agreement and as of the date of the closing of the merger, except for representations or warranties expressly made as of a specific date, the accuracy of which will be determined as of the specified date, except where any failure of such representations and warranties to be true and correct would not reasonably be expected to have, individually or in the aggregate, a material adverse effect on American Tower;

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American Tower and Asteroid Merger Sub having performed in all material respects all obligations required to be performed by them under the merger agreement at or prior to the consummation of the merger;

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each of American Tower and Asteroid Merger Sub having delivered to SpectraSite a certificate to the effect that each of the conditions specified above has been satisfied in all respects; and

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SpectraSite having received from Paul, Weiss, Rifkind, Wharton & Garrison LLP, counsel to SpectraSite, on the closing date of the merger, an opinion stating that the merger will be treated for U.S. federal income tax purposes as a “reorganization” within the meaning of Section 368(a) of the Internal Revenue Code and that SpectraSite and American Tower will each be a party to that reorganization within the meaning of Section 368(b) of the Internal Revenue Code.

Other than the conditions pertaining to stockholder approvals and the legality of the merger, either American Tower or SpectraSite may elect to waive conditions to its own performance and consummate the merger. However, neither American Tower nor SpectraSite will waive the closing condition regarding its receipt of an opinion of counsel regarding tax matters without resoliciting the approval of its stockholders after providing appropriate disclosure. Neither American Tower nor SpectraSite has any intention to waive any condition as of the date of this joint proxy statement/prospectus.

Representations and Warranties

The merger agreement contains customary representations and warranties of American Tower, Asteroid Merger Sub and SpectraSite, including representations and warranties relating to, among other things:

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corporate organization, good standing and similar corporate matters;

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capitalization;

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due authorization, execution, delivery and enforceability of the merger agreement and the transactions contemplated thereby;

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required stockholder vote of the stockholders of each of American Tower and SpectraSite;

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the receipt of fairness opinions from their respective financial advisors;

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absence of conflicts with the companies’ respective governing documents, applicable laws or material contracts;

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required consents, approvals, orders and authorizations of governmental authorities relating to the merger agreement and the transactions contemplated thereby;

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compliance with laws and regulatory compliance;

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documents filed with the SEC, compliance with applicable SEC filing requirements and accuracy of information contained in such documents;

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absence of any liabilities that are material to the respective companies, other than liabilities disclosed in the companies’ SEC documents, liabilities incurred in the ordinary course of business consistent with past practice since January 1, 2005 and other liabilities that were not or would not reasonably be expected to be material and adverse to the business of the respective companies;

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absence of material changes or events, including the absence of any event or occurrence that has had or would reasonably be expected to have a material adverse effect with respect to either company since January 1, 2005;

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filing of tax returns and payment of taxes;

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absence of change in control payments to employees or directors;

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pending or, to the knowledge of the companies, threatened litigation;

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specified contracts and commitments, and the enforceability of such contracts and commitments;

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accuracy of information supplied by each of American Tower and SpectraSite in connection with this joint proxy statement/prospectus and the registration statement of which it is a part;

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employee benefit plans and matters relating to ERISA;

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labor and employment matters;

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compliance with environmental laws and regulations;

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ownership and use of intellectual property;

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the absence of stockholders’ rights agreements;

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engagement and payment of fees of brokers, finders and investment bankers, other than their independent financial advisors;

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insurance; and

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no violation of the Foreign Corrupt Practices Act and related matters.

The merger agreement provides that a material adverse effect means, any change, effect, event, occurrence, state of facts or development that individually or in the aggregate have resulted in, or would reasonably be expected to result in, any change or effect, that (1) is materially adverse to the business, financial condition or results of operations of American Tower and its subsidiaries, taken as a whole, or SpectraSite and its subsidiaries, taken as a whole, or (2) prevents or has a material adverse effect on the ability of American Tower or SpectraSite, as applicable, to consummate the merger. None of the following, either alone or in combination, will constitute, and none of the following will be taken into account in determining whether there has been or will be, a material adverse effect:

(1)

any change relating to the United States or foreign economy or financial, credit or securities markets in general;

(2)

any change, in and of its itself, in the trading price or trading volume of American Tower Class A common stock or SpectraSite common stock;

(3)

any adverse change, effect, event, occurrence, state of facts or development reasonably attributable to conditions affecting the industry in which American Tower and SpectraSite participate;

(4)

any change in GAAP or the accounting rules and regulations of the SEC;

(5)

any change in laws of general applicability or interpretation of a law by any governmental entity;

(6)

any change resulting from departures of officers or employees of American Tower or SpectraSite resulting from the announcement of the merger;

(7)

any outbreak or escalation of major hostilities in which the United States is involved or any act of terrorism within the United States or directed against its facilities or citizens wherever located; or

(8)

any change to the business of SpectraSite or the surviving company resulting from the forward merger of SpectraSite into Asteroid Merger Sub and the surviving company’s subsequent compliance with the merger agreement covenant regarding contribution of assets and liabilities to a limited liability company wholly owned by American Tower;

provided that in the case of (1), (3), (4), (5) and (7) above, such effect does not disproportionately impact or uniquely relate to American Tower or SpectraSite, as the case may be.

Conduct of Business by American Tower and SpectraSite Prior to Consummation of the Merger

American Tower and SpectraSite have agreed that during the period from the date of the merger agreement to the earlier of the consummation of the merger and the termination of the merger agreement in accordance with its terms, unless American Tower or SpectraSite, as the case may be, consents in writing, each of American Tower and SpectraSite will conduct its business in the ordinary course of business in all material respects and in a manner consistent with past practice in all material respects and will use commercially reasonable efforts to preserve intact its business organizations, to keep available the services of its current officers and key employees and to preserve in all material respects its current relationships with customers, suppliers and other persons with which they have business dealings.

Further, except as previously disclosed to American Tower or SpectraSite, as applicable, in each respective company’s 2005 budget or otherwise, American Tower and SpectraSite will not, between the date of the merger agreement and the earlier of the consummation of the merger and the termination of the merger agreement in accordance with its terms, unless American Tower or SpectraSite, as the case may be, consents in writing:

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declare or pay any dividends on, or make other distributions in respect of, any of its capital stock, except for specified dividends by subsidiaries;

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subdivide, reclassify, recapitalize, split, combine or exchange any of its capital stock or issue or authorize or propose the issuance of any other securities in respect of, in lieu of or in substitution for, shares of its capital stock;

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repurchase, redeem or otherwise acquire any shares of its capital stock, other than pursuant to any repurchase obligations contained in benefit plans;

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issue, deliver or sell, or authorize, propose or reserve for issuance, delivery or sale of, any shares of its capital stock or any securities convertible into any such shares of its capital stock or any stock appreciation rights, phantom stock plans or stock equivalents, other than the issuance of shares upon the exercise of stock options or warrants outstanding as of the date of the merger agreement;

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take any action that would, or would reasonably be expected to, result in any of the conditions to consummation of the merger contained in the merger agreement not being satisfied;

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amend its certificate of incorporation or by-laws or other equivalent organizational documents;

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create, assume or incur indebtedness for borrowed money or guaranty any such indebtedness of another person, in a net aggregate amount of $10,000,000 with respect to SpectraSite and $18,600,000 with respect to American Tower;

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make any material loans or advances to any other person, other than loans to employees, excluding officers, or advances to employees, in each case made in the ordinary course in all material respects or intercompany loans or advances;

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other than in the ordinary course of business consistent with past practice, sell, lease, license, sell and leaseback, mortgage, pledge or otherwise encumber any of its assets or properties;

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make any acquisitions that involves a purchase price that (1) with respect to SpectraSite, individually, involves a purchase price in excess of $10,000,000 or, in the aggregate, involves a purchase price in excess of $25,000,000; or (2) with respect to American Tower, individually, involves a purchase price in excess of $18,600,000 or, in the aggregate, involves a purchase price in excess of $46,500,000;

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change its accounting policies except as required by law or GAAP;

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modify or amend in any material respect or terminate or cancel or enter into any material contract;

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other than in the ordinary course of business, pay, loan or advance, any amount to, or sell, transfer or lease any properties or assets to, any of its officers or directors or any “affiliate” or “associate” of any of its officers or directors;

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make any new capital expenditures (1) with respect to SpectraSite, individually, in excess of $5,000,000 or, in the aggregate, in excess of $10,000,000; or (2) with respect to American Tower, individually, in excess of $9,300,000 or, in the aggregate, in excess of $18,600,000; or

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take any action that would prevent the parties from treating the merger as “reorganization” under Section 368 of the Internal Revenue Code.

In addition, SpectraSite has agreed that, except as previously disclosed to American Tower in SpectraSite’s 2005 budget or otherwise, SpectraSite will not between the date of the merger agreement and the earlier of the consummation of the merger or the termination of the merger agreement in accordance with its terms, unless American Tower consents in writing:

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other than as required by law or a SpectraSite benefit plan or as required to avoid adverse treatment under Section 409A of the Internal Revenue Code: (1) amend any of the terms or conditions of employment for any of its directors or officers; (2) alter, amend or create any obligations with respect to compensation, severance, benefits, change of control payments or any other payments to employees, officers, directors or affiliates of SpectraSite or enter into any new, or amend any existing, employment agreements, in each case, except with respect to employees, excluding officers, effected in the ordinary course of business consistent with past practices; or (3) make any change to SpectraSite benefit plans;

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other than in the ordinary course of business, form or commence the operations of any business or any corporation, partnership, joint venture, business association or other business organization or division thereof or enter into any new line of business that is material to SpectraSite and its subsidiaries, taken as a whole;

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make any material tax election, other than in the ordinary course of business consistent with past practice, or settle or compromise any material tax liability; or

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pay, discharge, settle or satisfy any claims, litigation, liabilities or obligations, other than in the ordinary course of business or to the extent subject to and not in excess of reserves that are disclosed in SpectraSite’s filed SEC reports that relate to the matter being paid, discharged, settled or satisfied in accordance with GAAP or that, individually or in the aggregate, are not material to SpectraSite and its subsidiaries, taken as a whole.

The merger agreement provides that prior to the consummation of the merger each party will confer in good faith on a regular and frequent basis regarding operational matters and the general status of ongoing operations. No party will waive any rights it may have under the merger agreement as a result of such consultations and nothing in the merger agreement will give either party, directly or indirectly, the right to control or direct the other party’s operations prior to the consummation of the merger.

No Solicitation

SpectraSite Obligations. The merger agreement provides that SpectraSite will not, nor shall it authorize or permit its subsidiaries or representatives to:

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solicit, initiate or encourage, or take any other action designed to, or which would reasonably be expected to, facilitate, any SpectraSite takeover proposal; or

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enter into, continue or otherwise participate in any discussions or negotiations regarding, or furnish to any person any information, or otherwise cooperate with, any SpectraSite takeover proposal.

The merger agreement provides further that, notwithstanding the restrictions described above, if at any time prior to the time SpectraSite stockholders have approved the SpectraSite merger proposal:

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SpectraSite receives a bona fide written SpectraSite takeover proposal that the SpectraSite board of directors determines in good faith, after consultation with outside counsel and a financial advisor of nationally recognized reputation, constitutes, or would reasonably be expected to lead to, a SpectraSite superior proposal; and

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such SpectraSite takeover proposal was not solicited after the date of the merger agreement, was made after the date of the merger agreement and did not otherwise result from a breach by SpectraSite of the no solicitation provisions of the merger agreement described in this section;

then SpectraSite may, if the SpectraSite board of directors determines in good faith, after consultation with outside counsel, that it is required to do so to comply with its fiduciary duties to the SpectraSite stockholders under applicable law, and subject to giving American Tower written notice of such determination:

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furnish information with respect to SpectraSite to the person making such SpectraSite takeover proposal; and

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participate in discussions or negotiations with the person making such SpectraSite takeover proposal regarding such SpectraSite takeover proposal.

The merger agreement provides that the term “SpectraSite takeover proposal” means:

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any inquiry, proposal or offer from any person relating to, or that would reasonably be expected to lead to, any direct or indirect acquisition or purchase, in one transaction or a series of transactions, of assets or businesses that constitute 20% or more of the revenues, net income, earnings before interest expense, taxes, depreciation and amortization, or the assets of SpectraSite and its subsidiaries, taken as a whole or 20% or more of any class of equity securities of SpectraSite;

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any tender offer or exchange offer that if consummated would result in any person beneficially owning 20% or more of any class of equity securities of SpectraSite; or

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any merger, consolidation, business combination, recapitalization, liquidation, dissolution, joint venture, binding share exchange or similar transaction involving SpectraSite pursuant to which any person or the stockholders of any person would own 20% or more of any class of equity securities of SpectraSite or of any resulting parent company of SpectraSite.

The merger agreement provides that the term “SpectraSite superior proposal” means a SpectraSite takeover proposal, provided that for purposes of being a SpectraSite superior proposal all references to 20% in the definition of “SpectraSite takeover proposal” will be references to 50%, which the SpectraSite board of directors determines in good faith, after consultation with outside counsel and a financial advisor of nationally recognized reputation, to be:

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more favorable to the SpectraSite stockholders than the merger, taking into account all relevant factors, including all the terms and conditions of such proposal and the merger agreement and changes to the terms of the merger agreement proposed by American Tower in response to such offer; and

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reasonably capable of being consummated, taking into account all financial, legal, regulatory and other aspects of such proposal.

The SpectraSite board of directors cannot:

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withdraw, qualify or modify in a manner adverse to American Tower or Asteroid Merger Sub, or publicly propose to withdraw, qualify or modify in a manner adverse to American Tower or Asteroid Merger Sub, the adoption, approval, recommendation or declaration of advisability by the SpectraSite board of directors of the merger agreement or the merger;

•

recommend, adopt, approve or declare advisable, or propose publicly to recommend, adopt, approve or declare advisable, any SpectraSite takeover proposal; or

•

adopt, approve, recommend or declare advisable, or propose to adopt, approve, recommend or declare advisable, or allow SpectraSite to execute or enter into, any letter of intent, memorandum of understanding, agreement in principle, merger agreement, acquisition agreement, option agreement, joint venture agreement, partnership agreement or other similar agreement constituting or related to, or that is intended to or would reasonably be expected to lead to, any SpectraSite takeover proposal.

Notwithstanding the foregoing, at any time prior to the time SpectraSite stockholders have approved the SpectraSite merger proposal, the SpectraSite board of directors may recommend, adopt, approve or declare advisable, or propose publicly to recommend, adopt, approve or declare advisable, any SpectraSite takeover proposal if its board of directors determines in good faith, after consultation with outside counsel, that it is required to do so to comply with its fiduciary duties to the SpectraSite stockholders under applicable law, except that no such change in recommendation may be made until after the fifth calendar day following American Tower’s receipt of written notice from SpectraSite advising American Tower that the SpectraSite board of directors intends to take such action and specifying the reasons for such action, including the terms and conditions of any SpectraSite superior proposal that is the basis of the proposed action. In determining whether to change its recommendation, the SpectraSite board of directors will take into account any changes to the terms of the merger agreement proposed by American Tower in response to SpectraSite’s notice of its recommendation change.

With respect to a SpectraSite takeover proposal, SpectraSite will:

•

promptly advise American Tower orally and in writing, and within 24 hours, of any SpectraSite takeover proposal or any inquiry that would reasonably be expected to lead to any SpectraSite takeover proposal, the material terms and conditions of any such SpectraSite takeover proposal or inquiry, including any changes, and the identity of the person making the SpectraSite takeover proposal or inquiry;

•

keep American Tower fully and promptly informed of the status and material details, including any changes, of any such SpectraSite takeover proposal or inquiry; and

•

provide to American Tower promptly after receipt or delivery copies of all correspondence and other written material provided to SpectraSite from any person that describes any of the terms or conditions of any SpectraSite takeover proposal.

Nothing in the merger agreement will prohibit SpectraSite from taking and disclosing to its stockholders a position contemplated by Rule 14(e)-2(a) or Rule 14(d)-9 promulgated under the Exchange Act or from making any disclosure to SpectraSite’s stockholders if, in the good faith judgment of the SpectraSite board of directors, after consultation with independent outside counsel, failure to so disclose would be inconsistent with applicable law, except that all actions taken or agreed to be taken by SpectraSite or the SpectraSite board of directors must comply with the no solicitation provisions described above.

American Tower Obligations. The merger agreement further provides that American Tower will not, nor shall it authorize or permit its subsidiaries or representatives to:

•

solicit, initiate or encourage, or take any other action designed to, or which would reasonably be expected to, facilitate, any American Tower takeover proposal; or

•

enter into, continue or otherwise participate in any discussions or negotiations regarding, or furnish to any person any information, or otherwise cooperate with, any American Tower takeover proposal.

The merger agreement provides further that, notwithstanding the restrictions described above, if at any time prior to the time American Tower stockholders have approved the American Tower merger proposal:

•

American Tower receives a bona fide written American Tower takeover proposal that the American Tower board of directors determines in good faith, after consultation with outside counsel and a financial advisor of nationally recognized reputation, constitutes, or would reasonably be expected to lead to, an American Tower superior proposal; and

•

such American Tower takeover proposal was not solicited after the date of the merger agreement, was made after the date of the merger agreement and did not otherwise result from a breach by American Tower of the no solicitation provisions of the merger agreement described in this section;

then American Tower may, if its board of directors determines in good faith, after consultation with outside counsel, that it is required to do so to comply with its fiduciary duties to the American Tower stockholders under applicable law, and subject to giving SpectraSite written notice of such determination:

•

furnish information with respect to American Tower to the person making such American Tower takeover proposal; and

•

participate in discussions or negotiations with the person making such SpectraSite takeover proposal regarding such American Tower takeover proposal.

The merger agreement provides that the term “American Tower takeover proposal” means:

•

any inquiry, proposal or offer from any person relating to, or that would reasonably be expected to lead to, any direct or indirect acquisition or purchase, in one transaction or a series of transactions, of assets or businesses that constitute 20% or more of the revenues, net income, earnings before interest expense, taxes, depreciation and amortization, or the assets of American Tower and its subsidiaries, taken as a whole or 20% or more of any class of equity securities of American Tower;

•

any tender offer or exchange offer that if consummated would result in any person beneficially owning 20% or more of any class of equity securities of American Tower; or

•

any merger, consolidation, business combination, recapitalization, liquidation, dissolution, joint venture, binding share exchange or similar transaction involving American Tower pursuant to which any person or the stockholders of any person would own 20% or more of any class of equity securities of American Tower or of any resulting parent company of American Tower.

The merger agreement provides that the term “American Tower superior proposal” means an American Tower takeover proposal, provided that for purposes of being an American Tower superior proposal all references to 20% in the definition of “American Tower takeover proposal” will be references to 50%, which the American Tower board of directors determines in good faith, after consultation with outside counsel and a financial advisor of nationally recognized reputation, to be:

•

more favorable to the American Tower stockholders than the merger, taking into account all relevant factors, including all the terms and conditions of such proposal and the merger agreement and changes to the terms of the merger agreement proposed by SpectraSite in response to such offer; and

•

reasonably capable of being consummated, taking into account all financial, legal, regulatory and other aspects of such proposal.

The American Tower board of directors cannot:

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withdraw, qualify or modify in a manner adverse to SpectraSite, or publicly propose to withdraw, qualify or modify in a manner adverse to SpectraSite, the adoption, approval, recommendation or declaration of advisability by the American Tower board of directors of the merger agreement or the merger;

•

recommend, adopt, approve or declare advisable, or propose publicly to recommend, adopt, approve or declare advisable, any American Tower takeover proposal; or

•

adopt, approve, recommend or declare advisable, or propose to adopt, approve, recommend or declare advisable, or allow American Tower to execute or enter into, any letter of intent, memorandum of understanding, agreement in principle, merger agreement, acquisition agreement, option agreement, joint venture agreement, partnership agreement or other similar agreement constituting or related to, or that is intended to or would reasonably be expected to lead to, any American Tower takeover proposal.

Notwithstanding the foregoing, at any time prior to the time American Tower stockholders have approved the American Tower merger proposal, the American Tower board of directors may recommend, adopt, approve or declare advisable, or propose publicly to recommend, adopt, approve or declare advisable, any American Tower takeover proposal if its board of directors determines in good faith, after consultation with outside counsel, that it is required to do so to comply with its fiduciary duties to the American Tower stockholders under applicable law, except that no such change in recommendation may be made until after the fifth calendar day following SpectraSite’s receipt of written notice from American Tower advising SpectraSite that the American Tower board of directors intends to take such action and specifying the reasons for such action, including the terms and conditions of any American Tower superior proposal that is the basis of the proposed action. In determining whether to change its recommendation, the American Tower board of directors will take into account any changes to the terms of the merger agreement proposed by SpectraSite in response to American Tower’s notice of its recommendation change.

With respect to an American Tower takeover proposal, American Tower will:

•

promptly advise SpectraSite orally and in writing, and within 24 hours, of any American Tower takeover proposal or any inquiry that would reasonably be expected to lead to any American Tower takeover proposal, the material terms and conditions of any such American Tower takeover proposal or inquiry, including any changes, and the identity of the person making the American Tower takeover proposal or inquiry;

•

keep SpectraSite fully and promptly informed of the status and material details, including any changes, of any such American Tower takeover proposal or inquiry; and

•

provide to SpectraSite promptly after receipt or delivery copies of all correspondence and other written material provided to American Tower from any person that describes any of the terms or conditions of any American Tower takeover proposal.

Nothing in the merger agreement will prohibit American Tower from taking and disclosing to its stockholders a position contemplated by Rule 14(e)-2(a) or Rule 14(d)-9 promulgated under the Exchange Act or from making any disclosure to American Tower’s stockholders if, in the good faith judgment of the American Tower board of directors, after consultation with independent outside counsel, failure to so disclose would be inconsistent with applicable law, except that all actions taken or agreed to be taken by American Tower or the American Tower board of directors must comply with the no solicitation provisions described above.

Termination of the Merger Agreement

The merger agreement may be terminated at any time prior to the consummation of the merger by the mutual written consent of American Tower, Asteroid Merger Sub and SpectraSite.

In addition, the merger agreement may be terminated by either American Tower or SpectraSite if:

•

the merger has not been consummated by May 3, 2006, except that the right to terminate the merger agreement on this basis will not be available to any party whose willful breach of a representation or warranty or willful failure to fulfill any covenant or agreement contained in the merger agreement has been a principal cause of, or resulted in, the failure of the merger to be consummated on or by May 3, 2006;

•

the American Tower stockholders have not approved the American Tower merger proposal at the American Tower special meeting at which the proper vote of the American Tower stockholders was taken;

•

the SpectraSite stockholders have not approved the SpectraSite merger proposal at the SpectraSite special meeting at which the proper vote of the SpectraSite stockholders was taken; or

•

if any restraining order, injunction or other judgment issued by any court or other government entity of competent jurisdiction prohibiting the consummation of the merger or other transactions contemplated by the merger agreement is in effect and has become final and nonappealable.

The merger agreement also may be terminated by American Tower:

•

if SpectraSite breaches or fails to perform in any material respect any of its representations, warranties, covenants or other agreements contained in the merger agreement, which breach or failure to perform gives rise to the failure to satisfy the closing conditions of the merger agreement and is incapable of being cured, or is not cured within 30 calendar days following receipt of written notice from American Tower of the breach or failure to perform;

•

at any time prior to obtaining the approval of the SpectraSite merger proposal by the SpectraSite stockholders, within ten days after the SpectraSite board of directors has changed, modified or withdrawn its recommendation for the merger or has recommended or approved any SpectraSite takeover proposal; or

•

at any time prior to obtaining the approval by the American Tower stockholders of the American Tower merger proposal, so that American Tower can accept and enter into a binding agreement with respect to an American Tower superior proposal, subject to American Tower’s compliance with the applicable no solicitation provisions of the merger agreement and American Tower’s payment of the American Tower termination fee.

The merger agreement also may be terminated by SpectraSite:

•

if American Tower or Asteroid Merger Sub breaches or fails to perform in any material respect any of their representations, warranties, covenants or other agreements contained in the merger agreement, which breach or failure to perform gives rise to the failure to satisfy the closing conditions of the merger agreement and is incapable of being cured, or is not cured within 30 calendar days following receipt of written notice from SpectraSite of the breach or failure to perform;

•

at any time prior to obtaining the approval by the American Tower stockholders of the American Tower merger proposal, within ten days after the American Tower board of directors has changed, modified or withdrawn its recommendation for the merger or has recommended or approved any American Tower takeover proposal; or

•

at any time prior to obtaining the approval of the SpectraSite merger proposal by SpectraSite stockholders, so that SpectraSite can accept and enter into a binding agreement with respect to a SpectraSite superior proposal, subject to SpectraSite’s compliance with the applicable no solicitation provisions of the merger agreement and SpectraSite’s payment of the SpectraSite termination fee.

Expenses and Termination Fees

All fees and expenses incurred in connection with the merger will be paid by the party incurring such fees or expenses, except that each of SpectraSite and American Tower will bear and pay one-half of the costs and expenses incurred in connection with:

•

the filing, printing and mailing of this joint proxy statement/prospectus, including SEC filing fees;

•

the filings of the premerger notification and report forms under the HSR Act, including filing fees;

•

the third party service provider fees and expenses, other than consent, amendment, waiver or tender offer fees, incurred by the parties to obtain an amendment and/or waiver, if any, of SpectraSite’s credit facility; and

•

third party costs and expenses, other than consent, amendment, waiver or tender offer fees, of the parties to obtain a consent, amendment or waiver, if any, of the indenture for, or in conducting a tender offer for, SpectraSite’s outstanding 8.25% Senior Notes due 2010.

American Tower will pay any fees with respect to any consent, amendment, waiver or tender offer of the parties to obtain any amendment, waiver and/or consent with respect to SpectraSite’s credit facility or SpectraSite’s outstanding 8.25% Senior Notes due 2010, which fees will only be payable upon consummation of the merger. American Tower will file any return with respect to, and will pay, any state or local taxes imposed on SpectraSite, including any penalties or interest, if any, which are attributable to the transfer of the beneficial ownership of SpectraSite’s real property as a result of the merger.

American Tower Fees. American Tower will pay SpectraSite a termination fee in the amount of $110.0 million if the merger agreement is terminated:

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By American Tower or SpectraSite because the American Tower stockholders have not approved the American Tower merger proposal at the American Tower special meeting at which the proper vote of the American Tower stockholders was taken and (1) after May 3, 2005 an American Tower takeover proposal is made to American Tower and such American Tower takeover proposal becomes publicly known or is made directly to the American Tower stockholders prior to the American Tower special meeting and, such American Tower takeover proposal has not been withdrawn at the time of the American Tower special meeting and (2) within 12 months after termination of the merger agreement, American Tower consummates an American Tower takeover proposal or enters into a definitive agreement to consummate an American Tower takeover proposal and thereafter consummates the American Tower takeover proposal.

•

By American Tower or SpectraSite because the merger has not been consummated by May 3, 2006, but only if the American Tower special meeting at which the proper vote is to be taken on the American Tower merger proposal has not been held, and (1) after May 3, 2005 an American Tower takeover proposal is made to American Tower or directly to the American Tower stockholders or becomes publicly known or any person has publicly announced an intention to make an American Tower takeover proposal and (2) within 12 months after such termination, American Tower consummates an American Tower takeover proposal or enters into a definitive agreement to consummate an American Tower takeover proposal and thereafter consummates the American Tower takeover proposal.

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By SpectraSite because the American Tower board of directors has changed, modified or withdrawn its recommendation for the merger or has recommended or approved any American Tower takeover proposal and (1) after May 3, 2005 an American Tower takeover proposal is made to American Tower or directly to the American Tower stockholders or becomes publicly known or any person has publicly announced an intention to make an American Tower takeover proposal and (2) within 12 months after termination of the merger agreement, American Tower consummates an American Tower takeover proposal or enters into a definitive agreement to consummate an American Tower takeover proposal and thereafter consummates the American Tower takeover proposal; or

•

By American Tower to accept and enter into a binding agreement with respect to an American Tower superior proposal at any time prior to obtaining the approval of the American Tower merger proposal by American Tower stockholders.

Solely for purposes of this section captioned “—Expenses and Termination Fees—American Tower Fees”, all references to 20% in the term “American Tower takeover proposal” will be deemed references to 50%.

American Tower will reimburse SpectraSite for its out-of-pocket expenses up to $10.0 million if the merger agreement is terminated by SpectraSite because American Tower or Asteroid Merger Sub breached or failed to perform in any material respect any of its representations, warranties, covenants or other agreements contained in the merger agreement, which breach or failure to perform would give rise to the failure of to satisfy the closing conditions of the merger agreement and is incapable of being cured, or is not cured, within 30 calendar days following receipt of written notice from SpectraSite of the breach or failure to perform.

SpectraSite Fees. SpectraSite will pay American Tower a termination fee in the amount of $110.0 million if the merger agreement is terminated:

•

By SpectraSite or American Tower because the SpectraSite stockholders have not approved the merger agreement at the SpectraSite special meeting at which the proper vote of the SpectraSite stockholders was taken and (1) after May 3, 2005 a SpectraSite takeover proposal is made to SpectraSite and such SpectraSite takeover proposal becomes publicly known or is made directly to the SpectraSite stockholders prior to the SpectraSite special meeting and, such SpectraSite takeover proposal has not been withdrawn at the time of the SpectraSite special meeting and (2) within 12 months after termination of the merger agreement, SpectraSite consummates a SpectraSite takeover proposal or enters into a definitive agreement to consummate a SpectraSite takeover proposal and thereafter consummates the SpectraSite takeover proposal.

•

By SpectraSite or American Tower because the merger has not been consummated by May 3, 2006, but only if the SpectraSite special meeting at which the proper vote is to be taken on the merger has not been held, and (1) after May 3, 2005 a SpectraSite takeover proposal is made to SpectraSite or directly to the SpectraSite stockholders or becomes publicly known or any person has publicly announced an intention to make a SpectraSite takeover proposal and (2) within 12 months after such termination, SpectraSite consummates a SpectraSite takeover proposal or enters into a definitive agreement to consummate a SpectraSite takeover proposal and thereafter consummates the SpectraSite takeover proposal.

•

By American Tower because the SpectraSite board of directors has changed, modified or withdrawn its recommendation for the merger or has recommended or approved any SpectraSite takeover proposal and (1) after May 3, 2005 a SpectraSite takeover proposal is made to SpectraSite or directly to the SpectraSite stockholders or becomes publicly known or any person has publicly announced an intention to make a SpectraSite takeover proposal and (2) within 12 months after termination of the merger agreement, SpectraSite consummates a SpectraSite takeover proposal or enters into a definitive agreement to consummate a SpectraSite takeover proposal and thereafter consummates the SpectraSite takeover proposal; or

•

By SpectraSite to accept and enter into a binding agreement with respect to a SpectraSite superior proposal at any time prior to the approval of the SpectraSite merger proposal by SpectraSite stockholders.

Solely for purposes of this section captioned “—Expenses and Termination Fees—SpectraSite Fees”, all references to 20% in the term “SpectraSite takeover proposal” will be deemed references to 50%.

SpectraSite will reimburse American Tower for its out-of-pocket expenses up to $10.0 million if the merger agreement is terminated by American Tower because SpectraSite breached or failed to perform in any material respect any of its representations, warranties, covenants or other agreements contained in the merger agreement,

which breach or failure to perform would give rise to the failure to satisfy the closing conditions of the merger agreement and is incapable of being cured, or is not cured, within 30 calendar days following receipt of written notice from American Tower of the breach or failure to perform.

Filings Under the HSR Act; Reasonable Best Efforts

SpectraSite and American Tower will use reasonable best efforts to:

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obtain all requisite approvals and authorizations for the merger under the HSR Act or any other federal, state or foreign antitrust or fair trade law;

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cooperate with each other in connection with any HSR Act or other antitrust filing or submission and in connection with any investigation or other inquiry, including any proceeding initiated by a private party;

•

promptly inform the other party of any communication received by such party from or given by such party to, the Antitrust Division of the Department of Justice, the Federal Trade Commission or any other governmental entity and of any material communication received or given in connection with any proceeding by a private party;

•

permit the other party, or the other party’s legal counsel, to review any communication given by it to, and consult with each other in advance of any meeting or conference with, the Department of Justice, the Federal Trade Commission or any other governmental entity or with any other person in connection with any proceeding by a private party; and

•

give the other party the opportunity to attend and participate in such meetings and conferences.

If any objections are asserted with respect to the merger under any law or if any suit is instituted by any governmental entity or any private party challenging the merger as violative of any law, each of American Tower and SpectraSite will use its reasonable best efforts to resolve any such objections or challenge as such governmental entity or private party may have to such transactions under such law so as to permit consummation of the transactions contemplated by the merger agreement.

SpectraSite and American Tower have agreed to enter into a settlement, undertaking, consent decree, stipulation or other agreement with a governmental entity regarding antitrust matters that requires a party to divest or hold separate any of its or its subsidiaries’ assets; provided, however, that neither SpectraSite nor American Tower will be required to agree to, or proffer to:

•

divest or hold separate any assets or any portion of any of American Tower’s or its subsidiaries’ business, after giving effect to the merger, or agree to any restriction, condition or other limitation on the conduct of their respective businesses, to the extent that doing so would reasonably be expected to have, individually or in the aggregate, a material adverse effect on the combined company; or

•

divest or hold separate any assets or any portion of any of its or its subsidiaries’ business or agree to any material restriction, condition or other limitation on the conduct of their respective businesses, or take any other similar action, that is not conditional on the consummation of the merger.

Indemnification and Insurance

American Tower and SpectraSite agreed that all rights to indemnification by SpectraSite existing in favor of each present and former director and officer of SpectraSite or its subsidiaries in effect on the date of the merger agreement as provided for in SpectraSite’s certificate of incorporation or by-laws or pursuant to any other agreements will survive the merger. Additionally, American Tower will maintain for a period of at least six years from the effective time of the merger and perform in a timely manner its obligations with respect to the foregoing indemnification obligations in favor of each present and former director and officer of SpectraSite or its subsidiaries.

In addition, American Tower has agreed to maintain in effect for a period of six years from and after the consummation of the merger the current directors’ and officers’ liability insurance policies of SpectraSite containing coverage at the same level maintained at or prior to the consummation of the merger. American Tower, however, will not be required to expend more than an amount per year equal to 200% of current annual premiums paid by SpectraSite for such insurance. If American Tower would be required to expend more than 200% of current annual premiums, it will obtain the maximum amount of such insurance obtainable by payment of annual premiums equal to 200% of current annual premiums.

Board of Directors of the Combined Company

American Tower has agreed to expand the size of its board of directors from six directors to ten directors. All six current members of the American Tower board of directors will continue to serve as directors of American Tower following the merger. Effective as of the consummation of the merger, American Tower will appoint to the American Tower board of directors Messrs. Clark and Biltz and two other directors from the SpectraSite board of directors, who will be designated by SpectraSite and must be reasonably acceptable to American Tower. If either or both of Messrs. Clark and Biltz are unwilling or unable to serve as a director of American Tower as of the consummation of the merger, then SpectraSite will designate another individual or individuals, as the case may be, from the board of directors of SpectraSite, who must be reasonably acceptable to American Tower, to serve on the American Tower board of directors. The terms of all members of the American Tower board of directors, including the SpectraSite directors appointed in connection with the merger, will expire at the next annual meeting of the American Tower stockholders, which will occur in 2006.

Consents and/or Amendments of Certain Bank Lenders

American Tower and SpectraSite agreed, in the event American Tower determines in its reasonable judgment that it is necessary or advisable in connection with the consummation of the merger, to use its reasonable best efforts to obtain, and/or cooperate in, any request for an amendment and/or waiver under the credit agreement of SpectraSite’s wholly owned operating subsidiary relating to SpectraSite’s $900.0 million senior secured credit facility, including an amendment to the definition of “change of control” to exclude the merger, and SpectraSite agreed to effect such other amendments to such credit agreement as American Tower reasonably requests. American Tower and SpectraSite also agreed that, in the event the parties are not successful in obtaining such amendment and/or waiver that is acceptable to American Tower, then each party will cooperate and use its respective reasonable best efforts to refinance and replace the SpectraSite credit agreement with a substitute credit facility that is, to the extent available in the marketplace, on substantially similar terms as those contained in the SpectraSite credit agreement and otherwise reasonably acceptable to American Tower.

Notwithstanding the foregoing, American Tower has the option, in its sole discretion and upon notice to SpectraSite, to elect to refinance or otherwise repay in full the SpectraSite credit agreement and terminate all obligations thereunder as of the effective time of the merger, and SpectraSite agreed, on its own behalf and on behalf of the SpectraSite wholly owned operating subsidiary party to the credit agreement, to cooperate with American Tower with respect to such refinancing or other repayment and any related financing arrangements including a replacement credit agreement.

Consent Solicitation; Supplemental Indenture; Tender Offer

American Tower and SpectraSite agreed that, if American Tower determines in its reasonable judgment that it is necessary or advisable in connection with the consummation of the merger, each of American Tower and SpectraSite will use its reasonable best efforts to, and/or will cooperate in:

•

obtaining any consents to, amendments to or waivers from the indenture governing SpectraSite’s outstanding 8.25% senior notes due 2010, including an amendment to the definition of the term “change of control” to exclude the transactions contemplated by the merger agreement, and each party agreed to cause to become effective at the effective time of the merger a supplemental indenture for SpectraSite’s senior notes to reflect such consents, amendments or waivers, or

•

conducting a tender offer, either on its own or in connection with a consent solicitation contemplated by the preceding bullet point, for SpectraSite’s senior notes that is conditioned upon consummation of the merger,

in each case, in form and substance as reasonably requested by American Tower and reasonably acceptable to SpectraSite.

Employees

Until 90 days following the merger, American Tower and Asteroid Merger Sub will not terminate any employee employed by SpectraSite immediately prior to the merger and will provide these employees with the same or better compensation, excluding equity based compensation, as in effect for each such employee immediately prior to the merger. These obligations of American Tower and Asteroid Merger Sub do not apply to Messrs. Clark, Biltz and Slaven or prevent American Tower or Asteroid Merger Sub from terminating any employee for cause. As discussed in the section captioned “PROPOSAL NUMBER ONE: THE MERGER PROPOSALS—Conflicts of Interests of SpectraSite Directors and Executive Officers in the Merger—Severance” beginning on page 64, Messrs. Clark, Biltz and Slaven will not continue their employment with American Tower following consummation of the merger.

For one year following the merger, American Tower and Asteroid Merger Sub will maintain compensation and employee benefit plans that provide compensation and benefits, excluding equity based compensation, to the retained SpectraSite employees that remain employed by American Tower or Asteroid Merger Sub that have a value comparable, in the aggregate, to the compensation and benefits provided by SpectraSite benefit plans in effect on May 3, 2005 for such retained employees.

To determine eligibility to participate in, and rights under, any employee benefit plan of American Tower, retained SpectraSite employees will receive credit for service with SpectraSite as if it had been completed with American Tower.

Amendment and Waiver

The merger agreement may be amended in writing by American Tower and SpectraSite as authorized by their respective boards of directors. However, after approval of the SpectraSite merger proposal by the SpectraSite stockholders and the American Tower merger proposal by the American Tower stockholders, no amendment may be made that, without further approval of the American Tower and SpectraSite stockholders, changes the amount or the form of the consideration to be delivered to the SpectraSite stockholders, or which by law requires the further approval of the American Tower or SpectraSite stockholders.

Prior to the consummation of the merger, either American Tower or SpectraSite may:

•

extend the time for the performance of any of the covenants, obligations or other acts of any other party to the merger agreement; or

•

waive any inaccuracy of any representations or warranties or compliance with any of the agreements, covenants or conditions of any other party or with any conditions to its own obligations.

The failure of any party to the merger agreement to assert any of its rights under the merger agreement or otherwise will not constitute a waiver of such rights. The waiver of any right with respect to particular facts and circumstances will not be a waiver with respect to any other facts and circumstances and each such right will be an ongoing right that may be asserted at any time and from time to time.

Governing Law

The merger agreement will be governed by and construed in accordance with the laws of the State of Delaware, without regard to principles of conflicts of law thereof.

AMERICAN TOWER DESCRIPTION OF CAPITAL STOCK

The description below summarizes important terms of American Tower’s capital stock. Because this section is a summary, it does not describe every aspect of American Tower’s capital stock. This summary is subject to and qualified in its entirety by reference to the provisions of American Tower’s certificate of incorporation.

General

The authorized capital stock of American Tower Corporation consists of 20.0 million shares of preferred stock, $.01 par value per share, 500.0 million shares of Class A common stock, $.01 par value per share, 50.0 million shares of Class B common stock, $.01 par value per share, and 10.0 million shares of Class C common stock, $.01 par value per share. Except as otherwise provided in American Tower’s certificate of incorporation, the holders of the outstanding shares of American Tower’s common stock are entitled to the following rights: one vote per share of Class A common stock, ten votes per share of Class B common stock and no votes per share of Class C common stock. In February 2004, all outstanding shares of American Tower’s Class B common stock and Class C common stock were converted into shares of Class A common stock on a one-for-one basis. Future issuances of Class B common stock are prohibited by American Tower’s certificate of incorporation. See the section captioned “—Common Stock” beginning on page 91.

Pursuant to American Tower Proposal Number Two, American Tower is seeking stockholder approval to amend and restate its certificate of incorporation in order to:

•

Increase the authorized number of shares of Class A common stock from 500.0 million shares to 1.0 billion shares;

•

Eliminate the authorized shares of Class B common stock and Class C common stock, of which none are currently outstanding;

•

Eliminate voting power limitations that were applicable to certain holders of Class B common stock, including American Tower’s former Chairman and Chief Executive Officer, Steven B. Dodge; and

•

Make other conforming changes in connection with the foregoing.

The following description does not reflect the foregoing proposed amendments. For a comparison of certain differences between the current organizational documents of American Tower and the organizational documents of American Tower if American Tower Proposal Number Two at the American Tower special meeting is approved, see the section captioned “COMPARISON OF RIGHTS OF AMERICAN TOWER STOCKHOLDERS AND SPECTRASITE STOCKHOLDERS” beginning on page 100. The full text of the proposed Amended and Restated Certificate of Incorporation is attached as Annex E to this joint proxy statement/prospectus.

Preferred Stock

American Tower’s board of directors will determine the designations, preferences, limitations and relative rights of the 20.0 million authorized and unissued shares of preferred stock. These include:

•

the distinctive designation of each series and the number of shares that will constitute the series,

•

the voting rights, if any, of shares of the series,

•

whether shares of the series will be entitled to receive dividends and, if so, the dividend rate on the shares of the series, any restriction, limitation or condition upon the payment of the dividends, whether dividends will be cumulative, and the dates on which dividends are payable,

•

the prices at which, and the terms and conditions on which, the shares of the series may be redeemed, if the shares are redeemable,

•

the purchase or sinking fund provisions, if any, for the purchase or redemption of shares of the series,

•