Geography of South Dakota of the federal or state government, such as Badlands National Park, Wind Cave National Park, and Custer State Park, are located in the state. In 2011, the population of South Dakota was estimated to be 824,082, and the state ranks fifth-lowest in both total population as well as population density in the United States. Sioux Falls, with a population of just over 170,000, is the largest city in the state. Rapid City ranks as South Dakota's second-largest city, and Pierre is the state capital. Historically a very agricultural state, the service and tourism sectors have grown in economic importance in
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