St. Thomas is an island in the United States Virgin Islands.
Rachel Elizabeth Dare asks Percy Jackson to accompany her when her family takes a three day trip to their Beach House on the island. Later, Percy Dreams of Rachel on a beach on the island, later she begs her father to go back to New York City in exchange for attending Clarion Ladies Academy.
- St. Thomas is the first location in a book to be in an overseas territory of the United States of America to appear in a series.
- The capital is the United States Virgin Islands, Charlotte Amalie, is located on the island.