The Railway Post Office (RPO) car was built for the Southern RR by the American Car & Foundry Company in 1927. While RPO #39 was used all over the Southern System, it finished its services on routes thru Knoxville. The car was donated to a Chattanooga RR museum and was bought by the Old Smoky Railroad Museum in 1992. Car #39 appeared in the movie Christy and also the TV series. The car has seen few updates. It retains the original standard RPO interior and wooden windows. The Postal Service contracted with the railroads to transport and sort the mail while in transit.