It courses through Sumter , Clarendon , and Williamsburg counties before merging with the Great Pee Dee River in Georgetown County .
The Black River is a 151 - mile - long ( 243 km ) blackwater river in South Carolina in the United States .
Black River courses through Sumter , Clarendon , and Williamsburg counties before merging with the Great Pee Dee River in Georgetown County .
The Black River is a 151 - mile - long ( 243 km ) blackwater river in South Carolina in the United States .