WITNESSETH

Exhibit 4.21

FIRST SUPPLEMENTAL INDENTURE

This FIRST SUPPLEMENTAL INDENTURE (this “Supplemental Indenture”) is dated as of June 28, 2004, among SPEEDWAY MOTORSPORTS INC., a Delaware corporation (the “Company”), TSI Management Company, LLC, a North Carolina limited liability company (“TSI”), Speedway TBA, Inc., a North Carolina corporation (“TBA”) (TSI and TBA each, a “Guaranteeing Subsidiary” and collectively, the “Guaranteeing Subsidiaries”), the other Guarantors (as defined in and listed on the signature pages to the Indenture referred to below) and U.S. BANK NATIONAL ASSOCIATION, as trustee under the Indenture referred to below (the “Trustee”).

WITNESSETH

WHEREAS, the Company and the Guarantors have heretofore executed and delivered to the Trustee an indenture dated as of May 16, 2003 (the “Indenture”), providing for the issuance in an aggregate principal amount of up to $230,000,000 of the Company’s 6 ³/4% Senior Subordinated Notes due 2013 (the “Notes”); and

WHEREAS, the Indenture provides that under certain circumstances the Guaranteeing Subsidiaries shall execute and deliver to the Trustee a supplemental indenture pursuant to which the Guaranteeing Subsidiaries shall unconditionally guarantee all of the Company’s Obligations under the Notes and the Indenture on the terms and conditions set forth herein (the “Note Guarantee”); and

WHEREAS, TSI and TBA are 100% indirectly owned by the Company; and

WHEREAS, pursuant to Section 9.01 of the Indenture, the Trustee is authorized to execute and deliver this Supplemental Indenture;

NOW THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt of which is hereby acknowledged, the Guaranteeing Subsidiaries and the Trustee mutually covenant and agree for the equal and ratable benefit of the Holders of the Notes as follows:

1. Capitalized Terms. Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture.

2. Agreement to Guarantee. Each Guaranteeing Subsidiary hereby agrees as follows (notwithstanding anything to the contrary in this Supplemental Indenture, such agreements of the Guaranteeing Subsidiaries shall be construed as identical to those agreements made by the Guarantors under the Indenture, and the obligations and rights of the Guaranteeing Subsidiaries hereunder shall be no more and no less than those of the Guarantors under the Indenture):

(a) Along with all Guarantors named in the Indenture, to jointly and severally unconditionally guarantee to each Holder of a Note authenticated and delivered by the Trustee and to the Trustee and its successors and assigns, irrespective of the validity and enforceability of the Indenture, the Notes or the obligations of the Company under this Supplemental Indenture, the Indenture or the Notes, that:

(i) the principal of and interest on the Notes will be promptly paid in full when due, whether at maturity, by acceleration, redemption or otherwise, and interest on the overdue principal of and interest on the Notes, if any, if lawful, and all other obligations of the Company to the Holders or the Trustee under this Supplemental Indenture, the Indenture or the Notes will be promptly paid in full or performed, all in accordance with the terms of this Supplemental Indenture, the Indenture and the Notes; and

(ii) in case of any extension of time of payment or renewal of any Notes or any of such other obligations, that same will be promptly paid in full when due or performed in accordance with the terms of the extension or renewal, whether at stated maturity, by acceleration or otherwise. Failing payment when due of any amount so guaranteed or any performance so guaranteed for whatever reason, the Guaranteeing Subsidiaries and the Guarantors will be jointly and severally obligated to pay the same immediately.

(b) The obligations of the Guaranteeing Subsidiaries hereunder and under the Indenture shall be unconditional, irrespective of the validity, regularity or enforceability of this Supplemental Indenture, the Notes or the Indenture, the absence of any action to enforce the same, any waiver or consent by any Holder of the Notes with respect to any provisions hereof, of the Indenture or of the Notes, the recovery of any judgment against the Company, any action to enforce the same or any other circumstance which might otherwise constitute a legal or equitable discharge or defense of a guarantor.

(c) The following is hereby waived by each Guaranteeing Subsidiary: diligence, presentment, demand of payment, filing of claims with a court in the event of insolvency or bankruptcy of the Company, any right to require a proceeding first against the Company, protest, notice and all demands whatsoever.

(d) This Note Guarantee shall not be discharged except by complete performance of the obligations contained herein, and in the Notes and the Indenture, and each Guaranteeing Subsidiary accepts all obligations of a Guarantor under the Indenture.

(e) If any Holder or the Trustee is required by any court or otherwise to return to the Company, a Guaranteeing Subsidiary or the Guarantors, or any Custodian, Trustee, liquidator or other similar official acting in relation to either the Company, a Guaranteeing Subsidiary or the Guarantors, any amount paid by any of them to the Trustee or such Holder, this Note Guarantee, to the extent theretofore discharged, shall be reinstated in full force and effect.

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(f) Each Guaranteeing Subsidiary agrees that it shall not be entitled to any right of subrogation in relation to the Holders in respect of any obligations guaranteed hereby and by the Indenture until payment in full of all obligations guaranteed hereby and by the Indenture.

(g) As between the Guarantors and the Guaranteeing Subsidiaries, on the one hand, and the Holders and the Trustee, on the other hand, (x) the maturity of the obligations guaranteed hereby and by the Indenture may be accelerated as provided in Article VI of the Indenture for the purposes of this Subsidiary Guarantee, notwithstanding any stay, injunction or other prohibition preventing such acceleration in respect of the obligations guaranteed hereby and by the Indenture, and (y) in the event of any declaration of acceleration of such obligations as provided in Article VI of the Indenture, such obligations (whether or not due and payable) shall forthwith become due and payable by the Guarantors and the Guaranteeing Subsidiaries for the purpose of this Note Guarantee.

(h) The Guaranteeing Subsidiaries and the Guarantors shall have the right to seek contribution from any non-paying Guarantor so long as the exercise of such right does not impair the rights of the Holders under the Guarantee.

(i) Notwithstanding anything to the contrary in this Supplemental Indenture or in Article XI of the Indenture, the aggregate amount of the Obligations guaranteed hereunder and under the Indenture by the Guaranteeing Subsidiaries shall be reduced to the extent necessary to prevent the Subsidiary Guarantee of the Guaranteeing Subsidiaries from violating or becoming voidable under any law relating to fraudulent conveyance or fraudulent transfer or similar laws affecting the rights of creditors.

3. Execution and Delivery. Each Guaranteeing Subsidiary agrees that the Subsidiary Guarantee set forth in Section 11.01 of the Indenture shall remain in full force and effect notwithstanding any failure to endorse on each Note a notation of such Note Guarantee.

4. Guaranteeing Subsidiaries May Consolidate, Etc. on Certain Terms.

(a) Except as set forth in Articles IV and V and Section 11.03 of the Indenture, nothing contained in this Supplemental Indenture, in the Indenture or in any of the Notes shall prevent any consolidation or merger of a Guaranteeing Subsidiary with or into the Company or shall prevent any sale or conveyance of the property of a Guaranteeing Subsidiary as an entirety or substantially as an entirety, to the Company.

(b) Except as set forth in Article IV of the Indenture, nothing contained in this Supplemental Indenture, in the Indenture or in any of the Notes shall prevent any consolidation or merger of a Guaranteeing Subsidiary with or into a corporation or corporations other than the Company (whether or not affiliated with such Guaranteeing Subsidiary), or successive consolidations or mergers in which a Guaranteeing Subsidiary or its successor or successors shall be a party or parties, or shall prevent any sale or conveyance of the property of a Guaranteeing Subsidiary as an entirety or substantially as an entirety, to a corporation other than the Company (whether or not affiliated with such Guaranteeing Subsidiary) authorized to acquire and operate

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the same; provided, however, that (i) each Guaranteeing Subsidiary hereby covenants and agrees that, upon any such consolidation, merger, sale or conveyance, the Subsidiary Guarantee, and the due and punctual performance and observance of all of the covenants and conditions of this Supplemental Indenture and the Indenture to be performed by such Guaranteeing Subsidiary, shall be expressly assumed (in the event that the Guaranteeing Subsidiary is not the surviving corporation in the merger) by supplemental indenture reasonably satisfactory in form to the Trustee, executed and delivered to the Trustee, by the corporation formed by such consolidation, or into which such Guaranteeing Subsidiary shall have been merged, or by the corporation which shall have acquired such property and (ii) immediately after giving effect to such transaction, no Default or Event of Default would exist. In case of any such consolidation, merger, sale or conveyance and upon the assumption by the successor corporation, by supplemental indenture, executed and delivered to the Trustee and satisfactory in form to the Trustee, of the Subsidiary Guarantee and the due and punctual performance of all of the covenants and conditions of this Supplemental Indenture and the Indenture to be performed by such Guaranteeing Subsidiary, such successor corporation shall succeed to and be substituted for such Guaranteeing Subsidiary with the same effect as if it had been named herein as a Guarantor. Such successor corporation thereupon may cause to be signed any or all of the Subsidiary Guarantees to be endorsed upon all of the Notes issuable under the Indenture which theretofore shall not have been signed by the Company and delivered to the Trustee. All of the Subsidiary Guarantees so issued shall in all respects have the same legal rank and benefit under the Indenture as the Subsidiary Guarantees theretofore and thereafter issued in accordance with the terms of the Indenture as though all of such Subsidiary Guarantees had been issued at the date of the execution of this Supplemental Indenture.

5. Releases.

(a) Concurrently with any sale of assets (including, if applicable, all of the capital stock or membership interests, as the case may be, of a Guaranteeing Subsidiary), any Liens in favor of the Trustee in the assets sold thereby shall be released; provided, that in the event of an Asset Sale, the Net Proceeds from such sale or other disposition are treated in accordance with the provisions of Section 4.10 of the Indenture. If the assets sold in such sale or other disposition include all or substantially all of the assets of a Guaranteeing Subsidiary or all of the capital stock or membership interests of a Guaranteeing Subsidiary, then such Guaranteeing Subsidiary (in the event of a sale or other disposition or all of the capital stock or membership interests of the Guaranteeing Subsidiary) or the corporation acquiring the property (in the event of a sale or other disposition of all or substantially all of the assets of the Guaranteeing Subsidiary) shall be released and relieved of its obligations under its Subsidiary Guarantee or Section 11.03 of the Indenture, as the case may be; provided, that in the event of an Asset Sale, the Net Proceeds from such sale or other disposition are treated in accordance with the provisions of Section 4.10 of the Indenture. Upon delivery by the Company to the Trustee of an Officers’ Certificate and an Opinion of Counsel to the effect that such sale or other disposition was made by the Company in accordance with the provisions of the Indenture, including without limitation Section 4.10 of the Indenture, the Trustee shall execute any documents reasonably required to evidence the release of such Guaranteeing Subsidiary from its obligations under its Subsidiary Guarantee.

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(b) Upon (a) the release by all holders of Senior Indebtedness and Guarantor Senior Indebtedness of all guarantees issued by a Guaranteeing Subsidiary relating to such Senior Indebtedness and Guarantor Senior Indebtedness and all Liens on the property and assets of such Guaranteeing Subsidiary relating to Senior Indebtedness and Guarantor Senior Indebtedness, then such Guaranteeing Subsidiary or (b) the designation of a Subsidiary as an Unrestricted Subsidiary in compliance with the terms of the Indenture, then such Guarantor shall be released and relieved of any obligations under its Subsidiary Guarantee. Upon delivery by the Company to the Trustee of an Officers’ Certificate and an Opinion of Counsel to the effect that either (a) all holders of Senior Indebtedness and Guarantor Senior Indebtedness have released all guarantees issued by such Guaranteeing Subsidiary and all Liens on the property and assets of such Guaranteeing Subsidiary relating to such Senior Indebtedness and Guarantor Senior Indebtedness, or (b) that a Subsidiary has been designated as an Unrestricted Subsidiary in compliance with the terms of the indenture, the Trustee shall execute any documents reasonably required in order to evidence the release of such Guaranteeing Subsidiary from its obligations under its Subsidiary Guarantee.

(c) In the event a Guaranteeing Subsidiary is not released from its obligations under its Subsidiary Guarantee pursuant to either of paragraphs (a) or (b) of this Section 5 or Section 11.04 of the Indenture, such Guaranteeing Subsidiary shall remain liable for the full amount of principal of and interest on the Notes and for the other obligations of any Guarantor under this Supplemental Indenture or the Indenture, respectively, as provided in Article XI of the Indenture.

6. Subordination of Note Guarantees. The obligations of a Guaranteeing Subsidiary under its Subsidiary Guarantee pursuant to this Supplemental Indenture and Article XI of the Indenture shall be junior and subordinated to the Guarantor Senior Indebtedness of such Guaranteeing Subsidiary on the same basis as the Notes are junior and subordinated to Senior Indebtedness. For the purposes of the foregoing sentence, the Trustee and the Holders shall have the right to receive and/or retain payments by a Guaranteeing Subsidiary only at such times as they may receive and/or retain payments in respect of the Notes pursuant to the Indenture, including Article X of the Indenture.

7. No Recourse Against Others. No past, present or future director, officer, employee, incorporator, stockholder, organizer, member or agent of a Guaranteeing Subsidiary, as such, shall have any liability for any obligations of the Company or any Guarantor under the Notes, the Subsidiary Guarantees, the Indenture or this Supplemental Indenture or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each Holder of the Notes by accepting a Note waives and releases all such liability. The waiver and release are part of the consideration for issuance of the Notes. Such waiver may not be effective to waive liabilities under the federal securities laws and it is the view of the Securities and Exchange Commission that such a waiver is against public policy.

8. NEW YORK LAW TO GOVERN. THE INTERNAL LAW OF THE STATE OF NEW YORK SHALL GOVERN AND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE BUT WITHOUT GIVING EFFECT TO APPLICABLE PRINCIPLES OF

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CONFLICTS OF LAW TO THE EXTENT THAT THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

9. Counterparts. The parties may sign any number of copies of this Supplemental Indenture. Each signed copy shall be an original, but all of them together represent the same agreement.

10. Effect of Headings. The Section headings herein are for convenience only and shall not affect the construction hereof.

11. The Trustee. The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made solely by the Guaranteeing Subsidiaries and the Company.

[Signatures begin on the following page.]

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IN WITNESS WHEREOF, the parties hereto have caused this First Supplemental Indenture to be duly executed and attested, all as of the date first above written.

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