The Fort Yuma Territorial Prison, which operated from 1876 to 1909, was hellish in many respects, but it also had more modern amenities than many homes in Yuma at the time, including electricity, plumbing, a large library and even a band. Several of the inmates were Mormons who were convicted for polygamy. Today, the site of the hilltop prison is an Arizona state park, with some surviving original features, such as the cellblock, and other features reconstructed. It's now a historical museum that not only is open for tours, but stages special events such as gunfights and ghost hunts.
If you go:
Open June 1 to September 30 Thursday through Monday 9:00 to 5:00. October 1 to May 31 Monday through Sunday 9:00 to 5:00.
Links:

220 North Prison Hill Road
Yuma, Arizona 85364 USA
Phone Numbers:
Fort Yuma Territorial Prison
+1 (928) 783-4771
+1 (928) 783-4771