Hanson County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 3,461. Its county seat is Alexandria. The county was founded in 1871 and organized in 1873. It was named for Joseph R. Hanson, clerk of the first legislature. The town of Alexandria became the county seat in 1880.
Hanson county is approximately 18 miles east to west and 24 miles north to south. There are 12 Townships and 4 towns, Alexandria, Emery, Farmer and Fulton.