To simulate wartime repairs of railroads the Claiborne-Polk Military Railroad was built. The railroad was about 50 miles long and had 25 bridges. It crosed the Red River and Calcasieu River.
It ran from Camp Claiborne -- on the Missouri Pacific south of Alexandria -- westward 48 miles to Camp Polk -- on the Kansas City Southern south of Leesville. Construction began on 4 September 1941 and the Golden Spike ceremony was held on 11 July 1942. In October 1942, the soldiers who had built the Claiborne-Polk Military Railroad shipped out to Iran, where they helped operate the Trans-Iranian Railroad. The foundation of the locomotive shop and other remnants can still be seen.

The CPMR began regular operations on September 20, 1942. It operated as a line-haul railroad offering both passenger and freight service. It had ten steam locomotives, six passenger cars, six cabooses, and 101 freight cars. Two passenger trains operated in each direction daily and one freight operated each way daily except Sunday. The line's passenger train was unofficially called The Green Hornet. The CPMR was even featured in a Saturday Evening Post article entitled The Worst Railroad on Earth.

The 725th and other ROBs referred to it as the `Crime and Punishment` RR. Built by the 711th ROB and Army engineers. The engines were 40 years old, and the freight cars, some not US made were two generations old. Some european cars had only 4 wheels and did not do well on curves. Derailments were so often that they pulled a crain to pick up derailed cars and repair the roadbed. Often, the crain even derailed. Sometimes the rails sunk under the swamp and cars were lost in the quicksand. More than one engineer reported seeing the rails swaying and vibrating for some time after the train had passed. It was reported that one engine was lost in the quicksand and is still there. In other cases the built on top of the lost equipment using it as a foundation.

The Big Cut bridge ran the railroad over the Red River and Gulf RR instead of crossing or connecting to it. You can still see the place where the railroads crossed along with the concrete footings. Both railroads are now abandoned

For more on tracing out the railroad on the ground see this railroad website. Great photos from the camp.