The Cooper River is a mainly tidal river in the U.S. state of South Carolina. The cities of Mt. Pleasant, Charleston, North Charleston, Goose Creek, Moncks Corner, and Hanahan are located along the river. Short and wide, the river is joined first by the blackwater East Branch and then farther downstream at the tidal Wando River. Almost immediately thereafter…The Cooper River is a mainly tidal river in the U.S. state of South Carolina. The cities of Mt. Pleasant, Charleston, North Charleston, Goose Creek, Moncks Corner, and Hanahan are located along the river. Short and wide, the river is joined first by the blackwater East Branch and then farther downstream at the tidal Wando River. Almost immediately thereafter, the Cooper River widens into its estuary and unites with the Ashley River to form the Charleston Harbor.