Will Whittkaer Photo, Collection of Paul C. Koehler
The Cotton Belt built two batches of Modified 1937 AAR box cars at its Pine Blukk, AR shops. The first batch was built in 1941 (33500-33699) and the second came in 1943 (33700-33849.) The cars used welded underframes. Fifty cars in the first group received Superior doors and all had Apex Tri-Lok running boards. Both had the rare Alternate Center Rivet (ACR) pattern on the sides. The extra row of rivets was necessary because additional structural posts were incoporated into the sides to compensate for the thinner steel of the side panels. This resulted in a distinctive and subtly different car side. The SP and UP also built AAR design cars that incorporated the ACR design.