McCook County lies in the southeastern portion of the State of South Dakota along US Interstate 90 between the major South Dakota cities of Mitchell and Sioux Falls. The centrally located City of Salem is the county seat and is located at the crossroads of US Highway 81 and SD Highway 38. The county is comprised of five incorporated communities (Bridgewater, Canistota, Montrose, Salem and Spencer) and sixteen townships. McCook County has 576 square miles and the population according to the 2020 census is 5,682. Read More.