The Virgin Islands are the western island group of the Leeward Islands, which are the northern part of the Lesser Antilles, and form the border between the Caribbean Sea and the Atlantic Ocean. Politically, the eastern islands form the British Virgin Islands and the western ones form the United States Virgin Islands. The British Virgin Islands is an overseas territory of the United Kingdom comprising Tortola, Virgin Gorda, Jost Van Dyke and Anegada. The U.S. Virgin Islands is an unincorporated organized territory of the United States comprising St. Croix, St. John, St. Thomas and Water Island. The Virgin Passage separates the U.S. Virgin Islands from the Spanish Virgin Islands of Vieques and Culebra, which are part of Puerto Rico. The United States dollar is the official currency on both the British and U.S. Virgin Islands.