Yankton is a city in and the county seat of Yankton County, South Dakota, United States.
Yankton had a population of 14,454 at the 2010 census and it is the principal city of the Yankton Micropolitan Statistical Area, which includes the entirety of Yankton County and which had an estimated population of 22,662 as of July 1, 2017. Yankton was the first capital of Dakota Territory. It is named for the Yankton tribe of Western Dakota people; Yankton is derived from the Dakota 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 States 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 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.
Owing to the early exploitation of Fort Hays Limestone for cement manufacture, including shipment of cement to the construction of the Panama Canal, Yankton once also had the nickname "Cement City".
Yankton is located at 42°52′54″N 97°23′33″W (42.881647, −97.392485). in southern South Dakota on the state's border with Nebraska. The city is located on one of the last free-flowing, natural stretches of the Missouri River; this segment of the river, between Gavins Point Dam four miles west of Yankton, and Ponca State Park in Nebraska, has been designated by the U.S. National Park Service as the Missouri National Recreational River.