Richland County is a county located in the U.S. state of South Carolina. As of the 2010 census, the population was 384,504, making it the second-most populous county in South Carolina, behind only Greenville County. The county seat is Columbia, the state capital. Richland County is part of the Columbia, SC Metropolitan Statistical Area. In 2010, the center of population of South Carolina was located in Richland County, in the city of Columbia.