Puerto Rico is an island.
An archipelago ( [ ɑːrkᵻˈpɛləɡoʊ ] ) , sometimes called an island group or island chain , is a chain , cluster or collection of islands . Puerto Rico ( Spanish for `` Rich Port '' ) , officially the Commonwealth of Puerto Rico ( Estado Libre Asociado de Puerto Rico , `` Free Associated State of Puerto Rico '' ) and briefly called Porto Rico , is an unincorporated territory of the United States located in the northeast Caribbean Sea . The island 's population is approximately 3.4 million . Four centuries of Spanish colonial government transformed the island 's ethnic , cultural and physical landscapes primarily with waves of African slaves , and Canarian , and Andalusian settlers .