Dorchester County is located in the U.S. state of South Carolina. As of the 2020 census, the population was 161,540. Its county seat is St. George. The county was created on February 25, 1897 by an act of the South Carolina General Assembly. Dorchester County is included in the Charleston-North Charleston, SC Metropolitan Statistical Area. It is i…Dorchester County is located in the U.S. state of South Carolina. As of the 2020 census, the population was 161,540. Its county seat is St. George. The county was created on February 25, 1897 by an act of the South Carolina General Assembly. Dorchester County is included in the Charleston-North Charleston, SC Metropolitan Statistical Area. It is in the Lowcountry region of South Carolina.