Castillo de San Marcos is a Landmark of American Colonization

Castillo de San Marcos is a "masonry star''-type fort that was built by the Spanish in the late seventeenth century in order to defend the city of St. Augustine, originally settled by the Spaniards in 1565. Maintained by the U.S. National Park Service, the fort is a U.S. National Monument and is on the National Register of Historic Places. It is also a designated Hispanic Heritage Site.

Construction of the Castillo de San Marcos was ordered in 1672 by Mariana, Queen Regent of Spain, after Saint Augustine was attacked by British pirate Robert Searle in 1668. Workers were transported from Havana, Cuba to assist in the building of the fort, which took twenty-three years to complete. The material used to build the fort is known as coquina, Spanish for "little shells.'' The coquina, shells bonded together with calcite to form a limestone-type building material, was brought to the site from Anastasia Island, now a popular tourist area. It remains the oldest masonry fort in North America and is an excellent example of the centuries-old system of bastion fortification, which included diamond- or angle-shaped formations onto which canons or other artillery were placed.

Castillo de San Marcos' claim to fame is that it was never defeated in battle, despite several sieges against it. British canons were said to have very little affect on the walls of the fort, and at times, the entire population of the city stayed safe within the confines of the fortification.

The British would eventually assume ownership of the Castillo de San Marcos in 1763 under provisions of the Treaty of Paris. They would rename it Fort Saint Mark. The Second Treaty of Paris gave it back to the Spanish in 1784, with whom it remained until Florida was ceded to the United States in 1819. The name was then changed to Ft. Marion.

During the Civil War, the fort was a Confederate stronghold and through the rest of its active duty, Ft. Marion served largely as a military prison. Today, it has become a popular tourist attraction, situated on about 2.5 acres in what is now downtown St. Augustine, Florida.

Visitors to the fortress may explore on their own or take advantage of ranger-led tours that depart several times a day and educate visitors on the history of the fort and the culture of the people that fought and were imprisoned there. Re-enactors are a common site at Castillo de San Marcos and often participate in weapons demonstrations and other historic presentations. A video is available for those who desire more in-depth knowledge about the history of the fort.

Castillo de San Marcos welcomes up to 2,000 visitors per day during the peak tourist months, which includes the summer and other school holiday times. Because the fort is old and in precarious condition, wheelchair accessibility is not always possible so visitors with disabilities may not be able to tour the entire site.