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                                                                    Exhibit 4.1

                             SUPPLEMENTAL INDENTURE

                                       OF

                                   GUARANTORS

         THIS SUPPLEMENTAL INDENTURE dated as of March 2, 2000 is delivered
pursuant to Section 10.04 of the Indenture dated as of November 15, 1996 (as
heretofore or hereafter modified and supplemented and in effect from time to
time, the "Indenture") among LAMAR MEDIA CORP., a Delaware corporation,
(formerly Lamar Advertising Company) certain of its subsidiaries ("Guarantors")
and STATE STREET BANK AND TRUST COMPANY, a Massachusetts banking corporation,
as Trustee ("Trustee") (all terms used herein without definition having the
meanings ascribed to them in the Indenture).

         The undersigned hereby agree that:

         1. The undersigned is a Guarantor under the Indenture with all of the
rights and obligations of a Guarantor thereunder.

         2. The undersigned hereby grants, ratifies and confirms the guarantee
provided for by Article Ten of the Indenture to guarantee unconditionally,
jointly and severally with the other Guarantors, to each Holder of a Note
authenticated and delivered by the Trustee, and to the Trustee on behalf of
such Holder, the due and punctual payment of the principal of (and premium, if
any) and interest on such Note when and as the same shall become due and
payable.

         3. The undersigned hereby represents and warrants that the
representations and warranties set forth in the Indenture, to the extent
relating to the undersigned as Guarantor, are correct on and as of the date
hereof.

         4. All notices, requests and other communications provided for in the
Indenture should be delivered to the undersigned at the address specified in
Section 12.02 of the Indenture.

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

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




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

                                   Guarantor:

                                   LAMAR ADVAN, INC.
                                   a Pennsylvania corporation

                                   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:

STATE STREET BANK AND TRUST
    COMPANY, as Trustee

By:      /s/ Carolina D. Altomos
         --------------------------

Title:   Assistant Vice President
       ----------------------------

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                        Additional Subsidiary Guarantors



Lamar Advertising of Iowa, Inc.
Interstate Logos, L.L.C.