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                                                                     EXHIBIT 4.1

                                LAMAR MEDIA CORP.

                             SUPPLEMENTAL INDENTURE


         THIS SUPPLEMENTAL INDENTURE dated as of July 20, 1999, is delivered
pursuant to Section 5.01 of the Indenture dated as of November 15, 1996 (as
heretofore or hereafter modified and supplemented and in effect from time to
time, (the "1996 Indenture") among LAMAR ADVERTISING COMPANY. ("the Company"), a
Delaware corporation, certain of its subsidiaries ("Guarantors") and STATE
STREET BANK & TRUST COMPANY, a trust company organized under the laws of the
Commonwealth of Massachusetts, as Trustee ("Trustee") (all terms used herein
without definition having the meanings ascribed to them in the 1996 Indenture).

         The undersigned hereby agrees that:

         1. Lamar Advertising Company has caused Lamar Holdings Merge Co. to
merge into Lamar Advertising Company under the laws of the State of Delaware
("Merger") and incident thereto caused the name of Lamar Advertising Company to
be changed to Lamar Media Corp.

         2. Lamar Media Corp., being the Surviving Entity under the Merger as
provided under the 1996 Indenture, continues to be a corporation organized and
existing under the laws of the State of Delaware.

         3. The Surviving Entity ratifies and confirms its obligations as the
"Company" under the 1996 Indenture and the securities issued thereunder.

         4. Lamar Media Corp. hereby represents and warrants that the
representations and warranties set forth in the 1996 Indenture as amended by
this Supplemental Indenture are correct on and as of the date hereof.

         5. The Guarantors of the Indenture, being the subsidiaries of the
Surviving Entities listed below, hereby confirm and ratify their Guarantees of
the 1996 Indenture and the Securities issued thereunder and acknowledge that
their Guarantees will continue to apply to the obligations of the Company under
the 1996 Indenture.

         6. All notices, requests and other communications provided for in the
1996 Indenture should be delivered to the respective parties hereto at the
following address:



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            Lamar Media Corp.
            Attn: Mr. Keith A. Istre
            Vice President - Finance
            P.O. Box 66338
            Baton Rouge, LA 70896

         7. A counterpart of this Supplemental Indenture may be attached to any
counterpart of the 1996 Indenture.

         8. This Supplemental Indenture shall be governed by and construed in
accordance with the laws of the State of New York.

         IN WITNESS WHEREOF, the undersigned has caused this Supplemental
Indenture to be duly executed as of the day and year first above written.

                                 Guarantors:

                                 LAMAR MEDIA CORP.
                                 INTERSTATE LOGOS, INC.
                                 THE LAMAR CORPORATION
                                 LAMAR ADVERTISING OF MOBILE, INC.
                                 LAMAR ADVERTISING OF COLORADO
                                   SPRINGS, INC.
                                 LAMAR ADVERTISING OF SOUTH
                                   MISSISSIPPI, INC.
                                 LAMAR ADVERTISING OF JACKSON, INC.
                                 LAMAR TEXAS GENERAL PARTNER, INC.
                                 LAMAR ADVERTISING OF SOUTH
                                   GEORGIA, INC.
                                 TLC PROPERTIES, INC.
                                 TLC PROPERTIES, II, INC.
                                 LAMAR PENSACOLA TRANSIT, INC.
                                 LAMAR ADVERTISING OF
                                   YOUNGSTOWN, INC.
                                 NEBRASKA LOGOS, INC.
                                 OKLAHOMA LOGO SIGNS, INC.
                                 MISSOURI LOGOS, INC.
                                 OHIO LOGOS, INC.
                                 UTAH LOGOS, INC.
                                 TEXAS LOGOS, INC.
                                 MISSISSIPPI LOGOS, INC.
                                 GEORGIA LOGOS, INC.
                                 SOUTH CAROLINA LOGOS, INC.
                                 VIRGINIA LOGOS, INC.
                                 MINNESOTA LOGOS, INC.
                                 MICHIGAN LOGOS, INC.
                                 NEW JERSEY LOGOS, INC.




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                                 FLORIDA LOGOS, INC.
                                 KENTUCKY LOGOS, INC.
                                 NEVADA LOGOS, INC.
                                 TENNESSEE LOGOS, INC.
                                 KANSAS LOGOS, INC.
                                 COLORADO LOGOS, INC.
                                 NEW MEXICO LOGOS, INC.
                                 LAMAR ADVERTISING OF HUNTINGTON-
                                   BRIDGEPORT, INC.
                                 LAMAR ADVERTISING OF PENN, INC.
                                 LAMAR ADVERTISING OF
                                   MISSOURI, INC.
                                 LAMAR ADVERTISING OF
                                   MICHIGAN, INC.
                                 LAMAR ELECTRICAL, INC.
                                 LAMAR ADVERTISING OF
                                   SOUTH DAKOTA, INC.
                                 LAMAR ADVERTISING OF WEST VIRGINIA, INC.
                                 LAMAR ADVERTISING OF
                                   ASHLAND, INC.
                                 AMERICAN SIGNS, INC.
                                 LAMAR OCI NORTH CORPORATION
                                 LAMAR OCI SOUTH CORPORATION
                                 LAMAR ADVERTISING OF
                                   GREENVILLE, INC.
                                 LAMAR ROBINSON, INC.
                                 LAMAR ADVERTISING OF
                                   KENTUCKY, INC.
                                 LAMAR ADVERTISING OF ROLAND, INC.


                                 By:  /s/ Keith Istre
                                      ------------------------------------------
                                      Keith Istre, Vice President - Financial




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                                 LAMAR TEXAS LIMITED
                                  PARTNERSHIP By Lamar Texas
                                  General Partner, Inc.
                                          Its general partner

                                 By:  /s/ Keith Istre
                                      ------------------------------------------
                                      Keith Istre, Vice-President-Financial

                                 LAMAR TENNESSEE, L.L.C.
                                   By The Lamar Corporation, its manager


                                 By:  /s/ Keith Istre
                                      ------------------------------------------
                                      Keith Istre, Vice-President-Financial


                                 LAMAR AIR, L.L.C.
                                   By The Lamar Corporation, its manager


                                 By:  /s/ Keith Istre
                                      ------------------------------------------
                                      Keith Istre, Vice-President-Financial


                                 TLC PROPERTIES, L.L.C.
                                   By TLC Properties, Inc., its manager


                                 By:  /s/ Keith Istre
                                      ------------------------------------------
                                      Keith Istre, Vice-President-Financial

                                   Attest:

                                 By:  /s/ James McIlwain
                                      ------------------------------------------
                                      James McIlwain, Secretary

Accepted:


STATE STREET BANK & TRUST COMPANY, as Trustee

By:  /s/ Andrew Sinasky
   ------------------------------------------
Title:  Assistant Vice President
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