Hughes County, South Dakota Hughes County, South Dakota Hughes County is a county located in the U.S. state of South Dakota. As of the 2010 census, the population was 17,022, making it the least populous capital county in the nation, and the twelfth-most populous county in South Dakota. Its county seat is Pierre, the state capital. The county was created in 1873 and organized in 1880. It was named for Alexander Hughes, a legislator. Hughes County is part of the Pierre, SD Micropolitan Statistical Area. According to the U.S. Census Bureau, the county has a total area of , of which is land and
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.