Document:

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                                                                     Exhibit 4.1

                             SUPPLEMENTAL INDENTURE

                      TO INDENTURE DATED DECEMBER 23, 2002

      THIS SUPPLEMENTAL INDENTURE dated as of April 5, 2004, is delivered
pursuant to Section 4.18 of the Indenture dated as of December 23, 2002 (as
heretofore or hereafter modified and supplemented and in effect from time to
time, the "2002 Indenture") among LAMAR MEDIA CORP., a Delaware corporation,
certain of its subsidiaries ("Guarantors") and WACHOVIA BANK OF DELAWARE,
NATIONAL ASSOCIATION, a national banking corporation, as Trustee ("Trustee")
(all terms used herein without definition having the meanings ascribed to them
in the 2002 Indenture).

      The undersigned hereby agree that:

      1.    The undersigned is a Guarantor under the 2002 Indenture with all of
the rights and obligations of Guarantors thereunder.

      2.    The undersigned has granted, ratified and confirmed, in the form and
substance of Exhibit B to the 2002 Indenture, the Guarantee provided for by
Article 10 of the 2002 Indenture.

      3.    The undersigned hereby represents and warrants that the
representations and warranties set forth in the 2002 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
2002 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 2002 Indenture.

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

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

                                   Guarantor:

                                   Lamar Canadian Outdoor Company,
                                   a Nove Scotia unlimited liability company

                                   By:  /s/ Kevin P. Reilly, Jr.
                                      -----------------------------------------
                                       Kevin P. Reilly, Jr., President

Attest:

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

Accepted:

WACHOVIA BANK OF DELAWARE
NATIONAL ASSOCIATION, as Trustee

By:    /s/ Brian K. Justice
   -----------------------------------
Title: Vice President

                                        2<PAGE>

                                                                    Exhibit 10.1

                                JOINDER AGREEMENT

      JOINDER AGREEMENT dated as of April 19, 2004, by the undersigned, Lamar
Canadian Outdoor Company, (the "Additional Subsidiary Guarantor"), in favor of
JP Morgan Chase Bank, as administrative agent for the Lenders party to the
Credit Agreement referred to below (in such capacity, together with its
successors in such capacity, the "Administrative Agent").

      Lamar Media Corp. (formerly Lamar Advertising Company), a Delaware
corporation (the "Borrower"), and certain of its subsidiaries (collectively, the
"Existing Subsidiary Guarantors" and, together with the Borrower, the "Securing
Parties") are parties to a Credit Agreement dated March 7, 2003 (as modified and
supplemented and in effect from time to time, the "Credit Agreement", providing,
subject to the terms and conditions thereof, for extensions of credit (by means
of loans and letters of credit) to be made by the lenders therein (collectively,
together with any entity that becomes a "Lender" party to the Credit Agreement
after the date hereof as provided therein, the "Lenders" and, together with
Administrative Agent and any successors or assigns of any of the foregoing, the
"Secured Parties") to the Borrower in an aggregate principal or face amount not
exceeding $1,200,000,000 (which, in the circumstances contemplated by Section
2.01(d) thereof, may be increased to $1,700,000,000). In addition, the Borrower
may from time to time be obligated to one or more of the Lenders under the
Credit Agreement in respect of one or more Swap Agreements under and as defined
in the Credit Agreement (collectively, the "Swap Agreements").

      In connection with the Credit Agreement, the Borrower, the Existing
Subsidiary Guarantors and the Administrative Agent are parties to the Pledge
Agreement dated March 7, 2003 (the "Pledge Agreement") pursuant to which the
Securing Parties have, inter alia, granted a security interest in the Collateral
(as defined in the Pledge Agreement) as collateral security for the Secured
Obligations (as so defined). Terms defined in the Pledge Agreement are used
herein as defined therein.

      To induce the Secured Parties to enter into the Credit Agreement, and to
extend credit thereunder and to extend credit to the Borrower under Swap
Agreements, and for other good and valuable consideration the receipt and
sufficiency of which are hereby acknowledged, the Additional Subsidiary
Guarantor has agreed to become a party to the Credit Agreement and the Pledge
Agreement as a "Subsidiary Guarantor" thereunder, and to pledge and grant a
security interest in the Collateral (as defined in the Pledge Agreement).

      Accordingly, the parties hereto agree as follows:

      Section 1. Definitions. Terms defined in the Credit Agreement are used
herein as defined therein.

      Section 2. Joinder to Agreements. Effective upon the execution and
delivery hereof, the Additional Subsidiary Guarantor hereby agrees that it shall
become a "Subsidiary Guarantor" under

                                       1
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and for all purposes of the Credit Agreement and the Pledge Agreement with all
the rights and obligations of a Subsidiary Guarantor thereunder. Without
limiting the generality of the foregoing, the Additional Subsidiary Guarantor
hereby:

            (i) jointly and severally with the other Subsidiary Guarantors party
      to the Credit Agreement guarantees to each Secured Party and their
      respective successors and assigns the prompt payment in full when due
      (whether at stated maturity, by acceleration or otherwise) of all
      Guaranteed Obligations in the same manner and to the same extent as is
      provided in Article III of the Credit Agreement;

            (ii) pledges and grants the security interests in all right, title
      and interest of the Additional Subsidiary Guarantor in all Collateral (as
      defined in the Pledge Agreement) now owned or hereafter acquired by the
      Additional Subsidiary Guarantor and whether now existing or hereafter
      coming into existence provided for by Article III of the Pledge Agreement
      as collateral security for the Secured Obligations and agrees that Annex 1
      thereof shall be supplemented as provided in Appendix A hereto;

            (iii) makes the representations and warranties set forth in Article
      IV of the Credit Agreement and in Article II of the Pledge Agreement, to
      the extent relating to the Additional Subsidiary Guarantor or to the
      Pledged Equity evidenced by the certificates, if any, identified in
      Appendix A hereto; and

            (iv) submits to the jurisdiction of the courts, and waives jury
      trial, as provided in Sections 10.09 and 10.10 of the Credit Agreement.

      The Additional Subsidiary Guarantor hereby instructs its counsel to
deliver the opinions referred to in Section 6.10(a)(iii) of the Credit Agreement
to the Secured Parties.

                                       2
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      IN WITNESS WHEREOF, the Additional Subsidiary Guarantor has caused this
Joinder Agreement to be duly executed and delivered as of the day and year first
above written.

                                      Lamar Canadian Outdoor Company
                                      a Nova Scotia unlimited liability company

                                      By: /s/ Kevin P. Reilly
                                          -------------------------------------
                                            Kevin P. Reilly
                                              President

Attested:

By: James R. McIlwain
    ------------------------------
    James R. McIlwain, Secretary

Accepted and agreed:

JP MORGAN CHASE BANK,
  as Administrative Agent

By: /s/ Joan M. Fitzgibbon
    -------------------------------
  Title: Managing Director

                                       3
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The undersigned hereby respectively pledges and grants a security interest in
the Pledged Equity and evidenced by the certificate listed in Appendix A hereto
and agrees that Annex 1 of the above-referenced Pledge Agreement is hereby
supplemented by adding thereto the information listed on Appendix A.

Lamar Media Corp., Issuee

By: /s/ Keith A. Istre
    -------------------------------
        Keith A. Istre
Title:  Vice President of Finance,

        Treasurer & CFO

                                       4
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Supplement to Annex 1

                                                 Appendix A to Joinder Agreement

<TABLE>
<CAPTION>
   Pledgor
   Ownership                  Issuer                  No. Shares                 Cert. No.      %
--------------------------------------------------------------------------------------------------
<S>                     <C>                <C>                                   <C>           <C>
Lamar Media             Lamar Canadian     1,300,000 shares of Common
   Corp.                Outdoor Company        stock, no par value                  3           65
</TABLE>

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