Folly Beach is a public city on Folly Island in Charleston County, South Carolina, United States. The population was 2,617 at the 2010 censu…Folly Beach is a public city on Folly Island in Charleston County, South Carolina, United States. The population was 2,617 at the 2010 census, up from 2,116 in 2000. Folly Beach is within the Charleston-North Charleston-Summerville metropolitan area and the Charleston-North Charleston Urbanized Areas.