Campbell County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 1,377, making it the fourth-least populous county in South Dakota. Its county seat is Mound City. The county was created in 1873 and organized in 1884. It was named for Norman B. Campbell, a Dakota Territory legislator in 1873 and son of General Charles T. Campbell.

South Dakota Highway 10 (SD 10) is a 175.945-mile (283.156 km) state highway in the north-central and northeastern portions of South Dakota, United States. It connects SD 1804 in Pollock with the Minnesota state line southeast of Sisseton.