Perkins County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 2,835. Its county seat is Bison. The county was established in 1908 and organized in 1909. It was named for Sturgis, South Dakota, official Henry E. Perkins.

The Grand River is a tributary of the Missouri River in South Dakota in the United States. The length of the combined branch is 110 mi (177 km). With its longest fork, its length is approximately 200 mi (320 km).