 In the 1920s and 1930s, the sugar industry, on which Vieques was totally dependent, went into decline due to falling prices and industrial unrest.Many locals were forced to move to mainland Puerto Rico or Saint Croix to look for work.In 1941, while Europe was in the midst of World War II, the United States Navy purchased or seized about two thirds of Vieques as an extension to the Roosevelt Roads Naval Station nearby on the Puerto Rican mainland.