The claim: (67 W62/Minuteman III warheads; 525 W87/MX [Peacekeeper] warheads), Cheyenne, 5,866 (missile field covers an additional 12,600 sq. miles)
What it really is: Francis E. Warren Air Force Base is one of three strategic missile bases in the United States, although many of the original solos have since been destroyed and are in private ownership. The base itself is locate right next to the city of Cheyenne, and is on flat, clear land, which would make it difficult to hide any structures that would be used for a prison camp.
Also, taking a look at it via Google Maps I can't really find anything that resembles a prison camp.