Leavenworth is the largest city and county seat of Leavenworth County, in the U.S. state of Kansas and within the Kansas City, Missouri Metropolitan Area. Located in the northeast portion of the state, it is on the west bank of the Missouri River. As of the 2010 census, the city population was 35,251.
Leavenworth, founded in 1854, was the first incorporated city in Kansas. The city is located south of Fort Leavenworth, the oldest active Army post west of the Mississippi, which was established in 1827 by Colonel Henry Leavenworth. Leavenworth is the home of many detention centers and prisons, including the Leavenworth federal prison for which the city is most famous, and several smaller jails and prisons, including the city and county jails, a Federal Detention Center, and the military's maximum security prison, the United States Disciplinary Barracks. The very large Kansas State Penitentary and a state medium security prison are also located nearby.
Beneath the city appears to be another one entirely: a recently publicized underground series of "vaults" is thought to have been used for commerce, fugitives, or slaves.