Castillo de San Marcos

Castillo de San Marcos in St. Augustine, Florida, is the oldest surviving masonry fort in the continental United States. Spain began construction on October 2, 1672, to plans by engineer Ignacio Daza, and the core was finished in 1695. It was built of coquina, a soft limestone made of cemented seashells, quarried at King’s Quarry on Anastasia Island and ferried across Matanzas Bay. The walls are on average about 3.7 m (12 feet) thick, up to 5.8 m (19 feet) on the seaward side, and just under 10 m (33 feet) high.

Coquina does not shatter but gives way under fire: cannonballs bounced off or lodged in the stone. In 1702 the fort withstood an English siege under James Moore while the town fell; in 1740 it survived a 27-day bombardment under Oglethorpe. The British called it Fort St. Mark, from 1821 it was Fort Marion; it became a National Monument in 1924 and regained its Spanish name in 1942. In the Civil War, Confederates took it without a fight in 1861; most of the guns were removed, and five cannons remained in the water battery.

The fort lies on the western shore of Matanzas Bay. The visit is self-guided; 47 steps lead up to the gun deck with views of the bay. According to AARP (2022), the small parking lot fills quickly on busy days; alternatively, walk 10 to 15 minutes from a garage. Opening hours change, so check them in advance at nps.gov/casa.