Charlestown, former city, now part of Boston, Middlesex co., E Mass., on Boston Harbor, between the Mystic and the Charles rivers; settled 1629, included in Boston 1874. The oldest part of Boston, it was the site of the U.S. navy yard (est. 1801, closed 1973) where the U.S.S. Constitution is moored. The battle of Bunker Hill was fought in the vicinity on June 17, 1775. Samuel Morse was born in Charlestown. The navy yard is now the site of residential and commercial developments, but the area's history is preserved as part of the Boston National Historical Park (see National Parks and Monuments (table)).