South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. South Dakota is the 17th most extensive, but the 5th least populous and the 5th least densely populated of the 50 United States. Once the southern portion of the Dakota Territory, South Dakota became a state on November 2, 1889. Pierre is the state capital and Sioux Falls, with a population of 153,000, is South Dakota's largest city.