Black Rock Harbor is located in Bridgeport, Connecticut on Long Island Sound. The Black Rock Harbor Light on Fayerweather Island marks the entrance to the harbor on its east, while St. Mary's by the Sea forms its western beachhead. Seaside Park runs along the northeastern part of the harbor. The harbor is the mouth of Cedar Creek. It is a protected harbor that developed as a trade port and shipbuilding center in the 18th century.