San Juan (; ,
Saint John) is the
capital and most populous
municipality in the
Commonwealth of
Puerto Rico, an unincorporated territory of the United States. As of the
2010 census, it had a population of 395,326 making it the
46th-largest city under the jurisdiction of the United States. San Juan was founded by
Spanish colonists in 1521, who called it
Ciudad de Puerto Rico ("Rich Port City"). Puerto Rico's capital is the second oldest European-established capital city in the Americas, after
Santo Domingo, in the
Dominican Republic. Several historical buildings are located in San Juan; among the most notable are the city's former defensive forts,
Fort San Felipe del Morro and
Fort San Cristóbal, and
La Fortaleza, the oldest executive mansion in continuous use in the Americas.