Corsica is a city in Douglas County, South Dakota, United States. The population was 561 at the 2020 census. Corsica was laid out in 1906…Corsica is a city in Douglas County, South Dakota, United States. The population was 561 at the 2020 census. Corsica was laid out in 1906. The town took its name from Corsica, the native land of a share of the railroad workers.