Built over 340 years ago from coquina, a light and porous shell-stone rock, Castillo de San Marcos National Monument symbolizes the clash between cultures which ultimately resulted in our uniquely unified nation. Originally a post of the Spanish Empire guarding the settlement of St. Augustine, the Castillo protected the sea route for treasure ships before being transferred from Spanish to British control and back again, all by treaty. Purchased by the United States in 1821, the Castillo—then called Fort Marion—was used by the U.S. army until 1899.
Today, the Castillo is both a product of and evidence to the multitude of political and technological forces that created competition for empire during the colonial era, as well as the enduring legacy of the craftsmanship and skill of the engineers, artisans, and laborers who built it. Visitors are free to explore fortress’ unique masonry, explore exhibits, and experience demonstrations from re-enactors in period dress.