This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Charleston County, South Carolina" – news · newspapers · books · scholar · JSTOR (June 2007) (Learn how and when to remove this template message) Charleston County U.S. county Charleston County Courthouse Charleston County Courthouse Map of South Carolina highlighting Charleston County Location within the U.S. state of South Carolina Map of the United States highlighting South Carolina South Carolina's location within the U.S. Coordinates: 32°49′N 79°54′W Country United States State South Carolina Founded 1769 Seat Charleston Largest city Charleston Area • Total 1,358 sq mi (3,520 km2) • Land 916 sq mi (2,370 km2) • Water 442 sq mi (1,140 km2) 33% Population (2010) • Total 350,209 • Estimate (2018) 405,905 • Density 260/sq mi (100/km2) Time zone UTC−5 (Eastern) • Summer (DST) UTC−4 (EDT) Congressional districts 1st, 6th Website www.charlestoncounty.org Charleston County is located in the U.S. state of South Carolina along the Atlantic coast. As of the 2010 census, its population was 350,209,[1] making it the third most populous county in South Carolina (behind Greenville and Richland counties). Its county seat is Charleston.[2] The county was created in 1901 by an act of the South Carolina State Legislature. Charleston County is included in the Charleston-North Charleston, SC Metropolitan Statistical Area.