Yankton is a city in, and the county seat of, Yankton County, South Dakota, United States. The population was 14,454 at the 2010 census. Yankton is the principal city of the Yankton Micropolitan Statistical Area, which includes the entirety of Yankton County, and which had an estimated population of 22,696 as of 2013. Yankton was the first capital of Dakota Territory. It is named for the Yankton tribe of Nakota (Sioux) Native Americans; Yankton is derived from the Nakota word I-hank-ton-wan (“the end village”). Yankton is located on the Missouri River just downstream of the Gavins Point Dam and Lewis and Clark Lake and just upstream of the confluence with the James River. The United State National Park Service’s headquarters for the Missouri National Recreational River are located in the city. The Human Services Center was established as a psychiatric hospital in 1882 and is on the National Register of Historic Places. Yankton is commonly referred to as the “River City”, due to its proximity to the Missouri River and the importance that the river played in the city’s settlement and development. Yankton has also earned the nickname, “Mother City of the Dakotas”, due to the early important role it played in the creation and development of the Dakota Territory, which later became the 39th and 40th U.S. states of North and South Dakota, respectively.