Charlestown is the oldest neighborhood in Boston, Massachusetts, United States. Originally called Mishawum by the Massachusett, it is located on a peninsula north of the Charles River, across from downtown Boston, and also adjoins the Mystic River and Boston Harbor. Charlestown was laid out in 1629 by engineer Thomas Graves, one of its early settlers, in the reign of Charles I of England. It was originally a separate town and the first capital of the Massachusetts Bay Colony.