Built in 1870, when Idaho was still a territory, the Old Idaho Penitentiary started as a single-cell building. Throughout the years, resident inmates were put to work quarrying nearby stone and constructing and designing new buildings to expand the penitentiary. The penitentiary eventually grew from the original single-cell building to one consisting of 15 buildings, housing over 600 inmates.
In 1973, after two serious riots over living conditions, the prisoners were relocated and the prison was closed. That same year, the penitentiary was placed on the National Register of Historic Places.
A museum has been built and tours are offered through the Idaho State Historical Society. One of the most popular displays at the museum is an impressive collection of historic arms and military memorabilia dating back to 3500 BCE.