In 1521, he returned to Florida in an effort to establish a Spanish colony on the island. However, hostile Native Americans attacked his expedition soon after landing, and the party retreated to Cuba, where Ponce de Leon died from a mortal wound suffered during the battle. Successful Spanish colonization of the peninsula finally began at St. Augustine in 1565 and in 1819 the territory passed into U.S. control under the terms of the Florida Purchase Treaty between Spain and the United States.