Document:

<PAGE>

                                                                     Exhibit 4.1

                             SUPPLEMENTAL INDENTURE

                                       OF

                                    GUARANTOR

         THIS SUPPLEMENTAL INDENTURE dated as of October 7, 2003, 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 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.

<PAGE>

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

                              Guarantor:

                              Premere Outdoor, Inc.
                              an Illinois 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:

WACHOVIA BANK OF DELAWARE
NATIONAL ASSOCIATION, as Trustee

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

                                       2
<PAGE>

                        Additional Subsidiary Guarantors

Ham Development Corporation

10 Outdoor Advertising, Inc.

Lamar California Acquisition Corporation<PAGE>

                                                                     Exhibit 4.2

                             SUPPLEMENTAL INDENTURE

                                       OF

                                    GUARANTOR

         THIS SUPPLEMENTAL INDENTURE dated as of October 7, 2003, is delivered
pursuant to Section 10.04 of the Indenture dated as of September 25, 1997 (as
heretofore or hereafter modified and supplemented and in effect from time to
time, the "Indenture") among LAMAR MEDIA CORP., a Delaware corporation, certain
of its subsidiaries ("Guarantors") and U.S. BANK NATIONAL ASSOCIATION, as
successor to 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 Guarantors 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.

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

<PAGE>

                                            Guarantor:

                                            Premere Outdoor, Inc.
                                            an Illinois corporation

                                            By: /s/ Keith A. Istre
                                                ----------------------------
                                                Keith A. Istre
                                                Vice President - Finance and
                                                Chief Financial Office

Attest:

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

Accepted:

U.S. BANK NATIONAL ASSOCIATION
as successor to State Street Bank and Trust
         Company, as Trustee

By: /s/ John A. Brennan
    ----------------------------------------
Title: Assistant Vice President

                                   Page 2 of 3
<PAGE>

                        Additional Subsidiary Guarantors

Ham Development Corporation

10 Outdoor Advertising, Inc.

Lamar California Acquisition Corporation

                                   Page 3 of 3<PAGE>

                                                                    EXHIBIT 10.1

                                JOINDER AGREEMENT

         JOINDER AGREEMENT dated as of October 7, 2003, by the undersigned,
Premere Outdoor, Inc., (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 $1,250,000,000 (which, in the circumstances contemplated by Section
2.01(d) thereof, may be increased to $1,750,000,000). 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 Hedging
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:

                                       1
<PAGE>

         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 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
<PAGE>

         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.

                                         Premere Outdoor, Inc.
                                         an Illinois corporation

                                         By: /s/ Keith A. Istre
                                             --------------------------------
                                             Keith A. Istre
                                             Vice President - Finance and
                                             Chief Financial Officer

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
<PAGE>

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 Advantage GP Company, LLC, Issuee

By: Lamar Central Outdoor, Inc.,
Its Managing Member

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

                                       4
<PAGE>

Supplement to Annex 1

                                                 Appendix A to Joinder Agreement

<TABLE>
<CAPTION>
  Pledgor
 Ownership          Issuer          No. Shares   Cert. No.            %
<S>          <C>                    <C>          <C>                  <C>
   Lamar     Premere Outdoor, Inc.    1,000         4                 100
 Advantage                          shares or
GP Company,                          common
   LLC                              stock, no
                                    par value
</TABLE>

                                       5
<PAGE>

                  SCHEDULE OF ADDITIONAL SUBSIDIARY GUARANTORS

<TABLE>
<CAPTION>
GUARANTOR*                                       DATE OF JOINDER AGREEMENT
----------                                       -------------------------
<S>                                              <C>
Ham Development Corporation                           October 7, 2003
10 Outdoor Advertising, Inc.                          October 21, 2003
Lamar California Acquisition Corporation              October 21, 2003
</TABLE>

*The supplements to Annex 1/Appendix A to the Joinder Agreements of each
additional guarantor are set forth below in their entirety.

                                       6
<PAGE>

           SUPPLEMENT TO HAM DEVELOPMENT CORPORATION JOINDER AGREEMENT

SUPPLEMENT TO ANNEX 1
                                                 APPENDIX A TO JOINDER AGREEMENT

<TABLE>
<CAPTION>
PLEDGOR OWNERSHIP              ISSUER         NO. SHARES       CERT. NO.     %
-----------------              ------         ----------       ---------     -
<S>                          <C>              <C>              <C>          <C>
Lamar Central Outdoor, Inc.  Ham Development  1,000 shares        5         100
                             Corporation      of common
                                              stock, no
                                              par value
</TABLE>

                                       7
<PAGE>

          SUPPLEMENT TO 10 OUTDOOR ADVERTISING, INC. JOINDER AGREEMENT

SUPPLEMENT TO ANNEX 1

                                                 APPENDIX A TO JOINDER AGREEMENT

<TABLE>
<CAPTION>
   PLEDGOR OWNERSHIP                 ISSUER               NO. SHARES  CERT. NO.   %
   -----------------                 ------               ----------  ---------   -
<S>                         <C>                           <C>         <C>        <C>
The Lamar Company, L.L.C.   10 Outdoor Advertising, Inc.    1000         1       100
</TABLE>

                                        8
<PAGE>

    SUPPLEMENT TO LAMAR CALIFORNIA ACQUISITION CORPORATION JOINDER AGREEMENT

SUPPLEMENT TO ANNEX 1
                                                 APPENDIX A TO JOINDER AGREEMENT

<TABLE>
<CAPTION>
     PLEDGOR OWNERSHIP              ISSUER             NO. SHARES    CERT. NO.   %
     -----------------              ------             ----------    ---------   -
<S>                          <C>                      <C>            <C>        <C>
Lamar Central Outdoor, Inc.  Lamar California         100 shares of     2       100
                             Acquisition Corporation  common stock,
                                                      $.01
                                                      par value
</TABLE>

                                        9

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