The Castillo de San Marcos was built by the Spanish to protect Florida from their English enemies. Construction began in 1672 and was designed by Engineer Ignacio Daza using the bastion system as its main design feature. It was finally completed 23 years later in 1695. The bastion system eliminated blind spots and created a crossfire system so that all areas are covered by at least two cannon. While the Fort did change hands five times it was only during peace time and was never defeated in battle.
During the first British siege in 1702 they would fire upon the fort and the cannonballs would either bounce off the coquina walls of the fort or be absorbed into the walls and re-enforcing them. During the night the Spanish soldiers would come and repair the plaster and repaint. Coquina is extremely resilient to bombardment because it is filled with air pockets and made it more compressible. You can find more information on the construction of the fort at the National Park Service Website. was able to withstand more than one siege due to the thickness of the walls which ranged from 12 to 19 feet. This made the fort look like it received no damage and led the British to believe that the fort was self repairing. The British finally surrendered when the Spanish fleet came to the fort’s aid and trapped them in the Bay of Matanzas. 1500 civilians plus the soldiers stayed inside the fort for 51 days. During this siege the town itself was burned to the ground but the Fort stood and remained in Spanish possession. The fort during this time had only one source of water which came from a well inside the Plaza de Armas which is pictured. The well itself is now filled in and covered now. The doors you see lead to soldiers quarters, storerooms, and armament rooms, a chapel, and holding cells for prisoners.
When the United States bought Florida from Spain in 1819 for five million dollars it was the last time that Castillo de San Marcos changed hands. The United States already in possession of a fort named St. Mark changed the name to Fort Marion after the famous Revolutionary War hero the Swamp Fox of South Carolina, Francis Marion. Fort Marion became a National Park in 1933. In 1942 Fort Marion’s name was changed back to its original name of Castillo de San Marcos to better represent its Spanish history.
Before it became a National Park the United States used the Castillo de San Marcos to hold prisoners such as Confederates during the Civil War. While Florida did secede from the Union St. Augustine remained a Union stronghold. They also used it to hold Native American prisoners from the West and during the Seminole Wars held the famous Native American Chief Osceola. Today you can visit the Castillo de San Marcos and at night various ghost tours make it a regular stop as a part of their program. It is said that the fort is haunted by a headless man who is thought to either be Osceola or a Spanish soldier who died when a cannon blew up.