The GM&O motor train for Kansas City prepares for its early morning departure from Bloomington, Illinois in March 1957. Power unit 2509 was built by the St. Louis Car Company in 1928 for the Chicago & Alton, with the Electro-Motive Corporation supplying the electrical-mechanical components. It entered service as the C&A M20 and was renumbered to Alton Railroad 6021, receiving its final number 2509 with the 1947 merger into the Gulf, Mobile & Ohio. As delivered, 2509 and other GM&O motor cars were powered by gasoline engines. However, they carried the U.S. Mail and, by mandate of the Post Office, were required to be converted to diesel engines by the end of 1949. No. 2509 was retired in 1962.