CASTILLO DE SAN MARCOS NATIONAL MONUMENT

site of the oldest masonry fort in the U.S., built by the Spaniards on Matanzas Inlet between 1672 and 1696 to protect the city of St. Augustine, in northeastern Florida, U.S. Established as Fort Marion National Monument in 1924, it was renamed in 1942. It has an area of 20 ac (8 ha). The fort is a bastioned structure of coquina (shell stone) with walls 30 ft (9 m) high and 12 ft thick, surrounded by a moat. It played an important role in the SpanishEnglish struggle for the Southeast (16501750) and was later held by the English (176383). After the U.S. acquired Florida in 1819, it served as a military prison.