South Carolina Historical Marker Program: The official website of the S.C. Historical Marker program. Includes information about how to apply for a state marker.
Historical Marker Database: Probably the most comprehensive site dealing with historical makers from across the United States. It is searchable by keyword, location, and topic. Most markers also include substantial supplementary material produced by users.
Historic Markers Across South Carolina: A private effort to catalog South Carolina’s historic markers, including a number of non-state markers. The site is key word searchable and also includes a county index. There are also resources discussing historical markers in other states in the southeast.