Calhoun County is a county in the U.S. state of South Carolina. As of the 2020 census, its population was 14,119, making it the third-least populous county in the state. Its county seat is St. Matthews. In terms of land area, it is also the smallest county in the state.

Lexington County is a county located in the U.S. state of South Carolina. As of the 2020 census, the population was 293,991. Its county seat and largest community is Lexington. The county was chartered in 1785 and was named in commemoration of Lexington, Massachusetts, the site of the Battle of Lexington in the American Revolutionary War. Lexington County is the sixth-most populous county in South Carolina by population and is part of the Columbia, SC Metropolitan Statistical Area. It is located in the Midlands region of South Carolina.