Elko is a town in Barnwell County, South Carolina, United States. According to the 2010 census the population was 193. Elko is located in northern Barnwell County at 33°22′50″N 81°22′46″W / 33.38056°N 81.37944°W. U.S. Route 78 passes through the center of the town, leading east 6 miles to Blackville and west 2 miles to Williston. South …Elko is a town in Barnwell County, South Carolina, United States. According to the 2010 census the population was 193. Elko is located in northern Barnwell County at 33°22′50″N 81°22′46″W / 33.38056°N 81.37944°W. U.S. Route 78 passes through the center of the town, leading east 6 miles to Blackville and west 2 miles to Williston. South Carolina Highway 37 crosses US 78 at the center of Elko, leading south 10 miles to Barnwell, the county seat, and northeast 10 miles to Springfield.