Isla de Vieques, is an island–municipality of Puerto Rico in the northeastern Caribbean, part of an island grouping sometimes known as the Spanish Virgin Islands. Like the rest of Puerto Rico, a United States Commonwealth, Vieques retains strong influences from 400 years of Spanish ownership. The island lies about 8 miles east of the Puerto Rican mainland, and measures about 21 miles long by 4 miles wide. Its two main towns are Isabel Segunda , the administrative center on the northern side of the island, and Esperanza on the southern side. At peak, the population of Vieques is around 10,000.