The Ashley River is a blackwater / tidal river in South Carolina, rising from the Wassamassaw and Great Cypress Swamps in western Berkeley County. It consolidates its main channel about five miles west of Summerville, widening into a tidal estuary just south of Fort Dorchester. The river then flows for approximately 17 miles along the historical banks of the City of North Charleston before reaching peninsular Charleston. The much wider Ashley joins the Cooper River off the Battery in Charleston to form Charleston Harbor before discharging into the Atlantic Ocean.