Saint Thomas is an island in the Caribbean Sea and with the islands of Saint John, Saint Croix, and Water Island a county and constituent district of the United States Virgin Islands (USVI), an unincorporated territory of the United States. Located on the island is the territorial capital and port of Charlotte Amalie. As of the 2000 census, the population of Saint Thomas was 51,181 about 47% of the US Virgin Island total. The district has a land area of 31.24 square miles (80.9 km2).