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 situated on the west bank of the Missouri River. The population was 35,420 at the 2000 census. 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 Marshals' 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. Leavenworth is also home to University of Saint Mary (Kansas), operated by the Sisters of Charity. Leavenworth is sister city to the city of Wagga Wagga in the Australian state of New South Wales as well as the city of Ōmihachiman, Japan. 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 slavery.