Charlestown is a neighborhood in Boston, Massachusetts, United States, and the oldest settlement in modern-day Boston. Also 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 waterways. Charlestown was laid out in 1629 by engineer Thomas Graves, one of its earliest settlers, during the reign of Charles I of England. It was originally a separate town and the first capital of the Massachusetts Bay Colony.