The oldest masonry fort in the continental United States, the Castillo de San Marcos is a great example of Spanish influence in architecture. The monument, built from human determination, reflects a history that is centuries of years old. Throughout its history, the Castillo de San Marcos has been closely intertwined with the city of St. Augustine. The fort and the town serve as constant reminders of the early Spanish empire in the New World. Given the architectural details, the fort ultimately took twenty-three years to build, from 1672 to 1695.
While Queen Mariana of Spain demanded the construction of the fort, it had no specific design. It was constructed of coquina, a virtually indestructible limestone composed of broken sea shells. The fort was built to protect the seaside town from enemy attacks and it prevailed. It consisted of deep interior rooms with vaulted ceilings, multiple gun decks for cannons, as well as a taller exterior wall. The fort prevailed through three hundred and thirty years of enemy attacks, as well as violent and aggressive storms.
Throughout the years, the fort has served as multiple things under multiple names. Under the Treaty of Paris, Britain gained control of the fort and changed its name to Fort St. Mark. With Britain being the dominate power, the fort was not kept in first rate condition. This remained until the American Revolution. During the war, St. Augustine became the capital of the British colony of East Florida. Improvements were started on the fort, including the reparation of the gates and walls.
During the revolution, the fort mainly served as a prison, holding revolutionary fighters captured in Charleston. After the war, the fort was returned to Spain, as well as Florida. The name was changed back to Castillo de San Marcos and was signed over to the United States in the Adams-Onis Treaty. Under American control, the fort again underwent a name change; this time to Fort Marion. Structurally, nothing changed to the fort during this time and it remained so. In 1942, the fort was given its original name and was later designated a Historic Civil Engineering Landmark.
The Castillo now serves as a popular attraction and occupies 2 and a half acres in Saint Augustine. Castillo de San Marcos is the most significant piece of Spanish architecture in the state of Florida. It is the oldest masonry fort in the continental United States and is beautifully preserved. Along with Fort Matanzas, Fort Mose, and reconstructed sections of city walls, the Castillo de San Marcos depicts the rich military history of the oldest city in the United States.