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 15 1976, when many of the suffixed state routes were eliminated, this route was redesignated as SD 123. South Dakota Highway 15Y (SD 15Y) was a short state highway in the northeastern part of the U.S. state of South Dakota. It was established in the early 1960s, from US 12 in Big Stone City to SD 15 southwest of Shady Beach. In 1976, it was redesignated as SD 109. South Dakota Highway 15 South Dakota Highway 15 (SD 15) is a state highway in the northeastern part of the U.S. state of South Dakota. It connects Clear Lake, Milbank, and Wilmot.