The Old Montana Prison operated as a state penitentiary from 1871 to 1979, when overcrowding and a series of violent incidents led to the construction of a modern facility outside town. The old cellblock, guard towers and perimeter walls have been preserved as a museum complex at the south end of Main Street and form the main reason most travellers stop in Deer Lodge.
Visitors can walk through the original cell tiers — still lined with narrow iron cells — through the exercise yard, and into the guard towers. The site also includes the Powell County Museum of Montana history, an automobile museum with over a hundred vintage vehicles, the Yesterday's Playthings doll museum and the Frontier Montana Museum of Old West artefacts. A combined ticket covers all of them. Open daily; admission charged.