LOCATION: Boise, Idaho
BACKSTORY: Ground broke on construction for the Idaho Territorial Penitentiary, as it was then called, in 1870. In 1872, the first inmates arrived. The facility, set on more than four acres, started as one building, and increased in size and scope over the years—with the help of inmates' labor—to a complex of several buildings including Cell Houses 1 through 5. The prison was run by the federal government until 1890, when Idaho transitioned from territory status into statehood.
In its later decades, the prison became known for being overcrowded and poorly maintained. Now referred to as "Old Pen," the facility was home, if you can call it that, to more than 13,000 inmates and the site of 10 executions over its 101-year existence. Riots in 1973 led to the closing of Old Pen, at which point the prisoners were moved to the Idaho State Correctional Institution, which opened in 1972.
By 1974, Old Pen was listed on the National Register of Historic Places.