On 12 March 1785, Marlboro County was established by the South Carolina General Assembly according to its powers as described in the 1778 Constitution of the State of South Carolina during the American Revolution. It was named for the Duke of Marlborough. The nascent county remained part of what was then known as Cheraws District until 1798, then in 1800 Marlboro became a district itself. Under the 1868 Constitution of the State of South Carolina, passed during the Reconstruction era, South Carolina districts became counties with home rule, where the legislative representatives from each county had additional powers as councillors of their county.