Aurora County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 2,747. The county was created in 1879, and was organized in 1881.

Sanborn County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 2,330. Its county seat and largest city is Woonsocket. The county was created by the Dakota Territorial legislature on May 1, 1883, with land partitioned from Miner County. It was fully organized by July 18, 1883.