Charles Mix County, South Dakota
Charles Mix County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 9,373. Its county seat is Lake Andes. The county was created in 1862 and organized in 1879. It was named for Charles Eli Mix, an official of the Bureau of Indian Affairs influential in signing a peace treaty with the local Lakota Indian tribes. The easternmost approximately 60% of the county comprises the Yankton Indian Reservation.
The Papineau Trading Post, whose building is now in Geddes, South Dakota, was an early county seat. Geddes tried to wrest the county seat from Wheeler in 1900, 1904, and 1908. The Charles Mix County Courthouse in Lake Andes was built in 1918.