Saint John is an island in the Caribbean Sea and a constituent district of the United States Virgin Islands (USVI), an unincorporated territory of the United States. St. John is located about 4 miles east of Saint Thomas, the location of the territory's capital, Charlotte Amalie, and 4 miles south and west of Tortola, part of the British Virgin Islands. It is 50.8 km² (19.61 sq mi) in area and has a population of 4,197 (2000 census).Because there are no airports on St. John, the only access to the island is by boat. The ferry service runs hourly from St. Thomas and daily from Tortola; regular ferries also operate from Virgin Gorda, Jost Van Dyke and Anegada. Approximately 60% of the island is protected as Virgin Islands National Park.