The Rocky Mountain Arsenal, now Rocky Mountain Wildlife Refuge, is northeast of Denver, and had several miles of track on its property at one time. These tracks are identified as Rocky Mountain Railcar and Railroad (RMRR) on the SPV's Rail Atlas of Colorado and Utah.
The tracks within the arsenal had connections to two mainlines: the Burlington Northern (former CB&Q) to the northwest at Commerce City, and to the Union Pacific to the south near Roydale. The entire property is fenced, and it appears that all track has been removed within the fenced area. The BN connection is completely removed, but some of the UP track is still in place to serve other industries between the arsenal property line and the UP main line.
Thanks to Mike Palmer for contributing information.
Some of the trackage has been sold for $1 to the City of Colordo Springs for the use of the Pikes Peak Historical Street Railway Foundation.
My father worked on army munitions trains between the arsenal and Cheyenne during WW II. He was older and already had two children, saving him from being sent overseas. He liked the west, asked my mom to move there (from Pennsylvania), but she didn't like the thought of colder winters. I'd be interested in any information folks might have about the army's use of the rail lines in that era.