South Dakota South Dakota South Dakota () is a U.S. state in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux Native American tribes, who compose a large portion of the population and historically dominated the territory. South Dakota is the seventeenth largest by area, but the fifth smallest by population and the 5th least densely populated of the 50 United States. As the southern part of the former Dakota Territory, South Dakota became a state on November 2, 1889, simultaneously with North Dakota. Pierre is the state capital and Sioux Falls, with a population
South Dakota Highway 391 South Dakota Highway 391 South Dakota Highway 391 (SD 391) is a state highway in the southwestern part of the U.S. state of South Dakota. It travels from Nebraska Highway 27 (N-27) at the Nebraska state line, southeast of Denby, to U.S. Route 18 (US 18) east-southeast of Denby. The highway is located entirely within Oglala Lakota County and in the Pine Ridge Indian Reservation. It is maintained by the South Dakota Department of Transportation (SDDOT), and is not part of the National Highway System. SD 391 begins at the Nebraska state line as a continuation of N-27 and travels