Second Amendment to Lease and Development Agreement

Exhibit 10.55

Second Amendment to Lease and Development Agreement

Between

St. Louis County Port Authority

And

Pinnacle Entertainment, Inc.

SECOND AMENDMENT TO LEASE AND DEVELOPMENT AGREEMENT

This SECOND AMENDMENT TO LEASE AND DEVELOPMENT AGREEMENT (“Amendment”) is made and entered into this 7th day of October, 2005 by and between the ST. LOUIS COUNTY PORT AUTHORITY, a public body corporate and politic of the State of Missouri (“Landlord”) and PINNACLE ENTERTAINMENT, INC., a Delaware corporation (“Tenant”).

RECITALS

A. Landlord and Tenant entered into a Lease and Development Agreement dated as of August 12, 2004 as amended pursuant to the letter agreement between the Landlord and the Tenant of even date therewith (collectively, the “Lease and Development Agreement”) pursuant to which the Tenant agreed, subject to the terms and conditions in the Lease and Development Agreement, to construct and develop the gaming and mixed use Project in unincorporated Lemay, Missouri (the “Project”), including an access route to the property for the Project (the “Project Roadway”).

B. Landlord and Tenant agreed in the Lease and Development Agreement to work together on the development and construction of the Project Roadway; including the assistance of the United States Air Force and the General Services Administration to obtain the defense mapping facilities (the “NIMA Site”).

C. The Landlord has been negotiating with the United States Air Force (the “Air Force”) and the General Services Administration (“GSA”) for the acquisition of the NIMA Site to be used by Landlord for the economic development of the Lemay area.

D. A portion of the NIMA Site will be used for the proposed Project Roadway to the Project.

E. The Landlord has incurred and will continue to incur certain costs in connection with the due diligence on the NIMA Site and the negotiation of the agreements related to the acquisition of the NIMA site, including attorneys fees, environmental due diligence and for outside consultants.

F. The Landlord and the Tenant desire to amend the Lease and Development Agreement to provide for the payment of the fees and costs of the due diligence and negotiation of the acquisition of the NIMA Site.

NOW, THEREFORE, in consideration of the mutual covenants and agreements of the parties contained herein, Landlord and Tenant agree to amend the Lease and Redevelopment Agreement as follows:

1. Capitalized Terms . Capitalized terms used herein and not otherwise defined shall have the meanings ascribed to them in the Lease and Development Agreement.

- 1 -

2. Payment of Fees .

(a) Tenant shall reimburse Landlord for the consulting fees and expenses of Donna Erat in an amount not to exceed $90,000 within 30 days of receipt of an invoice from Landlord for the same, which invoice shall include applicable supporting documentation from Donna Erat.

(b) Tenant shall reimburse Landlord for the consulting fees and expenses of Greenhorne & O’Mara hi an amount not to exceed $64,000 within 30 days of receipt of an invoice from Landlord for the same, which invoice shall include applicable supporting documentation from Greenhorne & O’Mara.

(c) Attached as Exhibit A is scope of services and rate schedule for the services to be performed by Spencer Fane Britt & Brown (“Spencer Fane”) with respect to the Landlord’s acquisition of the NIMA Site. Exhibit A is incorporated herein by reference and the scope of services and rates are approved by Tenant. Attached as Exhibit B is the scope of services and fees for the environmental due diligence to be performed by Environmental Operations, Inc. (“EOI”) on the NIMA Site. Exhibit B is incorporated herein by reference and the scope of services and fees are approved by Tenant. The Spencer Fane fees and expenses and the EOI fees and expenses are hereinafter collectively referred to as the “NIMA Site Fees.” Tenant shall reimburse Landlord for the NIMA Site Fees subject to Tenant’s review and approval of the written invoices submitted by Spencer Fane and EOI to Landlord for payment. Tenant shall make any objections to the invoices within 20 days of receipt or such invoices shall be deemed approved. Tenant shall reimburse Landlord within 30 days of its approval of such invoices. Tenant’s reimbursement of Spencer