CASTLETOWN, a town of the Isle of Man (Manx. Bully Cashtel), '0 m. S.W. of Douglas, by the Isle of Man railway. Pop. (1921) 1,898. It lies on both sides of a small harbour formed by the outflow of the Silver Burn into Castletown Bay. It was the legal capital of the island until 1862. In the centre of the town stands Castle Rushen, said to have been founded by the Dane Guthred, in 947-960, though the existing building is prob ably 14th century. Until the 18th century it was the residence of the lords of Man. The massive keep is square, and is sur rounded by an outer wall, with towers and a moat. The council chamber and court-house were built in 1644. In the neighbour hood of the castle is the Old House of Keys, where the members of the Manx parliament held their sessions until the removal of the seat of government to Douglas. King William's College, situ ated a mile to the north-east of Castletown, is the chief school in the island. A small shipping trade is maintained.