1 EXHIBIT 4.3 SUPPLEMENTAL INDENTURE TO INDENTURE DATED AUGUST 15, 1997 THIS SUPPLEMENTAL INDENTURE dated as of September 15, 1999, is delivered pursuant to Section 4.11 of the Indenture dated as of August 15, 1997 (as heretofore or hereafter modified and supplemented and in effect from time to time, the "1997 Indenture") among OUTDOOR COMMUNICATIONS, INC., a Delaware corporation, certain of its subsidiaries (the "Guarantors") and FIRST UNION NATIONAL BANK, a national banking corporation, as Trustee (the "Trustee") (all terms used herein without definition having the meanings ascribed to them in the 1997 Indenture). The undersigned hereby agree that: 1. The undersigned are Guarantors under the 1997 Indenture with all of the rights and obligations of the Guarantors thereunder. 2. The undersigned have granted, ratified and confirmed, in the form and substance of Exhibit B to the 1997 Indenture, the Guarantee provided for by Article XI of the 1997 Indenture. 3. The undersigned hereby represent and warrant that the representations and warranties set forth in the 1997 Indenture, to the extent relating to the undersigned as Guarantors, are correct on and as of the date hereof. 4. All notices, requests and other communications provided for in the 1997 Indenture should be delivered to the undersigned at the following address: Keith A. Istre Vice President - Finance and Chief Financial Officer Lamar Media Corp. and its Subsidiaries 5551 Corporate Blvd. Baton Rouge, LA 70808 5. A counterpart of this Supplemental Indenture may be attached to any counterpart of the 1997 Indenture. 6. This Supplemental Indenture shall be governed by and construed in accordance with the internal laws of the State of New York. 2 IN WITNESS WHEREOF, the undersigned have caused this Supplemental Indenture to be duly executed as of the day and year first above written. Guarantors: LAMAR MW SIGN CORPORATION LAMAR MARTIN CORPORATION LAMAR NEVADA SIGN CORPORATION LAMAR OUTDOOR CORPORATION LAMAR WHITECO OUTDOOR CORPORATION DOWLING COMPANY, INCORPORATED HARDIN DEVELOPMENT CORPORATION LINDSAY OUTDOOR ADVERTISING INC PARSONS DEVELOPMENT COMPANY REVOLUTION OUTDOOR ADVERTISING, INC. SCENIC OUTDOOR MARKETING & CONSULTING INC. WESTERN POSTER SERVICE, INC. By: /s/ Keith A. Istre ------------------------------------------ Keith A. Istre Vice President - Finance and Chief Financial Officer LAMAR WEST, L.P. By: Lamar MW Sign Corporation, Its General Partner By: /s/ Keith A. Istre ------------------------------------------ Keith A. Istre Vice President - Finance and Chief Financial Officer 2 3 OUTDOOR PROMOTIONS WEST, LLC TRANSIT AMERICA LAS VEGAS, L.L.C. TRIUMPH OUTDOOR LOUISIANA, LLC TRIUMPH OUTDOOR RHODE ISLAND, LLC By: Triumph Outdoor Holdings, LLC, its manager By: Lamar Outdoor Corporation, its manager By: /s/ Keith A. Istre ------------------------------------------ Keith A. Istre Vice President - Finance and Chief Financial Officer TRIUMPH OUTDOOR HOLDINGS, LLC By: Lamar Outdoor Corporation, its manager By: /s/ Keith A. Istre ------------------------------------------ Keith A. Istre Vice President - Finance and Chief Financial Officer Attest: By: /s/ James R. McIlwain --------------------------------------------------- James R. McIlwain, Secretary Accepted: FIRST UNION NATIONAL BANK, as Trustee By: /s/ Josie Gonot --------------------------------------------------- Title: Assistant Vice President Corporate Trust Group ------------------------------------------------ 3