Aiken County is a county in the U.S. state of South Carolina. As of the 2020 census, its population was 168,808. Its county seat and largest community is Aiken. Aiken County is a part of the Augusta-Richmond County, GA-SC Metropolitan Statistical Area. It is mostly in the Sandhills region, with the northern parts reaching in the Piedmont and souther…Aiken County is a county in the U.S. state of South Carolina. As of the 2020 census, its population was 168,808. Its county seat and largest community is Aiken. Aiken County is a part of the Augusta-Richmond County, GA-SC Metropolitan Statistical Area. It is mostly in the Sandhills region, with the northern parts reaching in the Piedmont and southern parts reaching into the Coastal Plain.