Castillo de San Marcos stands today as a monument to the Spanish empire’s 300-year occupation of Florida and to the interaction and clashes of cultural groups that built the unified nation that is the United States today. Constructed to protect Spain’s settlement in St. Augustine from pirate raids, hostile American Indian tribes, and neighboring imperial powers, the fortification is a symbol of the cultural and imperial struggles that shaped early North America. Never captured in battle, Castillo de San Marcos is both architecturally impressive as the oldest surviving masonry fortress in the United States and culturally significant because its stone walls are a testament to the endurance of this nation’s Latino heritage and to the other cultural groups that have played a role in its story.

Spanish influence in America began in 1513 when Juan Ponce de León, upon discovering the Florida peninsula, claimed North America for Spain. Recognizing the strategic significance of Florida for the defense of their treasure fleets, the Spanish began to settle the southeast coast of North America. Their efforts proved unsuccessful and costly, and in 1561, King Phillip II of Spain halted future expeditions into Florida. When news came three years later of the French settlement of Fort Caroline on the St. Johns River, the Spanish king revoked his order and commissioned Pedro Menéndez de Avilés to remove the French. By 1565, Menéndez and his crew established a settlement on a sheltered harbor they named San Agustín and reclaimed Florida for Spain when they launched a successful and ruthless attack on Fort Caroline.

Old City Gates into St. Augustine Courtesy of John Stavely through Flickr's Creative Commons

During the first century of occupation in St. Augustine, the Spanish were victims of numerous enemy attacks that destroyed their original wooden fortifications. The Spanish constructed a series of wooden fortifications until English privateer Sir Francis Drake seized St. Augustine in 1586. An English sailor who accompanied Drake on this expedition against Spain described St. Augustine (San Agustín) as a “city built all of timber…or bodies of trees set upright and close together.” Following Drake’s attack and a later raid in 1668 by pirate John Davis, the Spanish governor of the Florida colony wrote to officials in Spain and Mexico requesting funds to build a more permanent defense system. The Spanish crown approved plans to build a stone fortress, and, in 1672, construction of Castillo de San Marcos began.

The Spanish designed Castillo de San Marcos to withstand the impact of a cannonball, using the bastion system developed by Italians in the 17th century. Resembling the medieval castle, or castillo, the bastion design lowered the castle walls and placed mounds of earth around the exterior to reinforce the walls. At each corner of the castle walls, the Spanish -- aware of their vulnerability to land and water attacks -- placed a circular tower to protect the fortress from every angle. To secure access into the castle, the Spanish constructed drawbridges. The survival of the Castillo today demonstrates the strength and success of the bastion system.

The castle underwent minor changes during different periods of its occupation by the Spanish, English, and Americans. Under the Spanish, Castillo de San Marcos had four bastions, 30 feet high and 14 feet thick walls of coquina blocks -- a soft limestone made of cemented seashells. Although disease and funding shortages slowed construction, the Spanish were ready to test the true strength of the coquina fortress during the War of Spanish Succession. After an attack in 1702, Castillo de San Marcos was the only structure to survive the fire that the English set in St. Augustine. After this, the Spanish sought to defend the city by extending the castle with a system of inner defense lines. By 1763, the Spanish finished construction on the Cubo and Rosario Lines, which are still present today, to form a boundary around St. Augustine for protection from future land attacks.

Whenever St. Augustine was under siege, the Castillo de San Marcos courtyard served as a place of refuge for the city’s inhabitants. Courtesy of the National Park Service

When tensions increased during the War of Jenkins’ Ear, the conflict between Spain and England that lasted between 1739 and 1748, the Spanish governor in St. Augustine wrote to officials in Cuba requesting funds, supplies, laborers, and soldiers to help extend the height of the walls, build an underground powder magazine, and replace the original ravelin. In 1763, after completion of most of the renovations, news came of the Spanish cession of Florida to England in the treaty that ended the Seven Years’ War. The Spanish surrendered the Castillo de San Marcos to England and abandoned St. Augustine altogether.

During the first decade of British occupation, the English renamed the fortification Fort St. Mark. Victorious at the end of the French and Indian War, the British did not seek to restore the fortress knowing they had eliminated all other competing imperial powers from North America’s eastern coast. Repairs and changes to the structure did not occur until the outbreak of the American Revolution when British loyalists sought refuge within Fort St. Mark’s walls. The British garrison reconstructed the former entrenchment lines and used the fort to house troops, weapons, and to imprison rebel colonists. Although the Continental Army planned to attack the British in east Florida, Fort St. Mark did not see any action during the American Revolution and remained unharmed throughout the remainder of the British occupation.

In 1784, the brief British control of St. Augustine ended when negotiations at the end of the war returned Florida to Spain. Throughout the second Spanish occupation of St. Augustine, Castillo de San Marcos was the center of a diverse cultural exchange. When the Spanish returned to Florida, they welcomed into St. Augustine American Indians, slaves, free blacks, British colonists, and immigrants from Italy, Greece, Germany, France, and Ireland. The new Spanish St. Augustine was not a peaceful city, however. Castillo de San Marcos found itself vulnerable to attacks from plantation owners from northern Georgia who crossed over to find and capture fugitive slaves. The Spanish, fearing future attacks from the Americans, continued to make improvements to the fortress, but American encroachment into Florida proved difficult to combat, and in 1821, Spain ceded Florida to the United States.

Castillo de San Marcos Gun Deck Courtesy of Mark Revers through Flickr's Creative Commons

Under the new American occupation, Castillo de San Marcos became the property of the United States War Department. President James Monroe, believing the Florida acquisition would calm relations with Seminole Indians, appointed Andrew Jackson to govern St. Augustine at the newly named Fort Marion. Castillo San Marcos (now Fort Marion) was by that time uninhabitable from disrepair. The fortress became a storage facility for military supplies until the outbreak of the Second Seminole War in 1835. By 1842, Army engineers had modified the fort with a water battery, furnace, and refilled the moat around the castle walls. With the repairs, Castillo de San Marcos served as an active defensive fortification during the Seminole and western Indian wars, serving its purpose a final time during the American Civil War.

At the end of Reconstruction, with the resort and railroad land developments in Florida by tycoon Henry Flagler, St. Augustine and the Castillo de San Marcos became a popular tourist destination. The War Department offered guided tours, and in 1883 -- having recognized the value of the historic fort -- made a request for Congressional support to restore the fort. Now managed by the National Park Service, the Castillo illustrates the resourcefulness of the Spanish and their capable military engineers in the New World and the history and cultural influences of various groups associated with the site. Visitors can explore the fortress, enjoy a ranger program, watch a video, or view a demonstration by re-enactors.