EXHIBIT 4.203 State of Delaware Secretary of State Division of Corporations Delivered 05:35 PM 12/15/2003 FILED 05:12 PM 12/15/2003 SRV 030806686 - 0941815 FILE CERTIFICATE OF CONVERSION FROM A CORPORATION TO A LIMITED LIABILITY COMPANY PURSUANT TO SECTION 266 OF THE DELAWARE GENERAL CORPORATION LAW 1. The name of the corporation is PEABODY DEVELOPMENT COMPANY. - The name under which the corporation was originally incorporated is PREMIER COAL SALES COMPANY. 2. The date on which the original Certificate of Incorporation was filed with the Secretary of State is July 28, 1982. 3. The name of the limited liability company into which the corporation is herein being converted is PEABODY DEVELOPMENT COMPANY, LLC. 4. This Certificate of Conversion shall be effective on December 16, 2003. 5. The conversion has been approved in accordance with the provisions of Section 266. By /s/ JOSEPH W. BEAN --------------------------- Authorized Officer NAME: JOSEPH W. BEAN --------------------------- PRINT OR TYPE NAME