Castletown is a town in the Isle of Man. In 2001, the population was 3100 inhabitants. Castletown is the historical capital of the island. Castletown is located in the south of the island, on the coast. It is known the Castletown already existed in 1090. It used to be the capital of the island before Douglas. Rushen Castle, now a museum, was founded in the 13th century. There is a small harbour. Castletown is served by the Isle of Man steam railway. The only airport of the island, Isle of Man airport, is located near Castletown.