Leavenworth Prison, a federal penitentiary. It is on the grounds of Fort Leavenworth, Kansas, an army post. The prison occupies about 1,000 acres (400 hectares) on a plot three miles (5 km) north of the city of Leavenworth. Leavenworth Prison was established in 1895. It houses about 3,000 inmates, who work in the prison factories or on one of the two farms.