Marshall County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 4,306. Its county seat is Britton. The county was created on May 2, 1885, and was named for Marshall Vincent, who homesteaded near Andover, South Dakota.

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.