Castillo de San Marcos
National Monument
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Outpost of Empire

Castillo de San Marcos was for many years the northernmost outpost of Spain's vast New World empire. It is the oldest masonry fort and the best-preserved example of a Spanish colonial fortification in the continental United States. It anchored East Florida's defenses, which extended northward to the St. Marys River, westward to the St. Johns, and southward to Fort Matanzas. It protected St. Augustine from pirate raids and from Spain's major rival, Great Britain, during time when the Florida-Georgia-Carolina coastline was an explosive international battleground.

The roots of the Castillo's history reach back to the years just after Christopher Columbus's final transatlantic voyage, when conquistadores carved out a vast and wealthy overseas empire for Spain, first in the Caribbean and then on the mainlands of Mexico, Central America, Colombia, Venezuela, and Peru. Products of these tropical and mountainous territories brought high prices on the Continent, and Spanish galleons sailed home laden with exotic dyes, sugar, tobacco, chocolate, pearls, hardwoods, and silver and gold. These so-called "treasure fleets" made Spain the most powerful and envied nation in Renaissance Europe.

Thanks to the travels of Ponce de Leon in 1513, Spanish navigators knew that the best return route from Spain's rich Caribbean possessions was along the Gulf Stream, through the Bahama Channel, and past the shores of Florida. The Spanish knew they must defend this peninsula to prevent enemies from using its harbors as havens from which to raid the passing treasure fleets.

In 1513 Spain claimed Florida through the expedition of Ponce de Leon, but France gained the first foothold there by establishing Fort Caroline on the St. Johns River in 1564. Seeing this as both a challenge to Spain's claims and a menace to the treasure fleets, King Philip II sent an expedition under Don Pedro Menéndez de Avilés to eliminate the French threat and establish settlements in Florida. It arrived at the mouth of the St. Johns River in September 1565.

After attempting unsuccessfully to board the French ships anchored there, Menéndez sailed to a harbor farther south and established St. Augustine as a base for further operations. Almost immediately a French fleet sailed south to attack. But the ships were driven southward and wrecked by a violent storm and the mission failed. Realizing that Fort Caroline would be lightly guarded, the Spaniards marched north, captured the fort, and executed most of the inhabitants. The same fate befell survivors from the French fleet, whom the Spaniards captured and killed at an inlet 14 miles south of St. Augustine. The episode gave a name to the area: Matanzas, Spanish for "slaughters."

England became Spain's next contender for Florida. The Spanish had watched the English warily ever since Sir Francis Drake attacked and burned St. Augustine in 1586. They became even more watchful after Englishmen settled Jamestown in 1607. British pirates sacked St. Augustine again in 1668, and this hit-and-run attack, followed by the English settlement of Charleston in 1670, caused Spain to build the Castillo de San Marcos.

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Begun in 1672 and completed by 1695, the Castillo replaced nine successive wooden fortifications that had protected St. Augustine since its founding. The fort's commanding location on the west bank of Matanzas Bay allowed its guns to protect not only the harbor entrance but the ground to the north against a land attack.

The Castillo's baptism of fire came in 1702 during the War of the Spanish Succession, when the English occupied St. Augustine and unsuccessfully besieged the fort for 50 days. The English burned the town before they left, but the Castillo emerged unscathed, thereby making it a symbolic link between the old St. Augustine of 1565 and the new city that rose from the ashes.

To strengthen the defenses, the Spanish erected new earthwork lines on the north and west sides of St. Augustine, thus making it a walled city. Matanzas Inlet, however, was still unfortified when Gen. James Oglethorpe's British troops from Fort Frederica in Georgia attacked St. Augustine in 1740. Again the Castillo was besieged and Matanzas Inlet blockaded. But the Spanish did not waver during the 27-day British bombardment. The attack also taught the Spanish the strategic value of Matanzas Inlet and the need for a strong outpost there. Consequently, in 1742, they completed the present coquina tower.

In 1763, as an outcome of the Seven Years' (French and Indian) War, Spain ceded Florida to Great Britain in return for La Habana, Cuba. The British garrisoned Matanzas and strengthened the Castillo, holding the two forts through the American Revolution. The Treaty of Paris of 1783, which ended the war, returned Florida to Spain.

Spain held Florida until 1821, when serious Spanish-American tensions led to its cession to the United States. The Americans renamed the Castillo Fort Marion and used it to house Indian prisoners during the Seminole War of 1835-42. Confederate troops occupied it briefly during the Civil War and Indians captured in western military campaigns were held there later on. It was last used during the Spanish-American War as a military prison.

Castillo Timeline

The key dates, arranged by century, are important to the story of the development of the Castillo de San Marcos, whose coquina walls are silent reminders of Spain's contributions to Florida and U.S. history.

16th Century

1513 Sailing from Puerto Rico, Spanish claim Florida.

1565 Spanish found St. Augustine and destroy French at Fort Caroline and Matanzas Inlet.

17th Century

1672 Ground is broken on October 2 for Castillo de San Marcos.

1695 Castillo de San Marcos (curtain walls, bastions, living quarters, moat, ravelin, and seawall) is finished in August.

18th Century

1702 War of the Spanish Succession pits Spain and France against Austria, Great Britain, and others.

Coastal Georgia missions are destroyed by Carolinians en route to St. Augustine.

Carolinians occupy and burn St. Augustine but the Castillo successfully resists their siege.

1738 Spanish governor at St. Augustine grants freedom to runaway British slaves. Black families settle at new town called Fort Mose.

1740 St. Augustine successfully endures siege by British, Georgian, and South Carolinian forces.

Spanish attack and defeat British Highland troops camped at Fort Mose.

1740-42 Fort Matanzas is built to block southern approach to St. Augustine.

1756-62 Fort Mose rebuilt in masonry. Earthworks at Mose extended to complete northernmost defense.

1763 Peace of Paris gives Florida to Great Britain in exchange for La Habana.

Castillo becomes known as Fort St. Mark.

1783 Peace of Paris recognizes independence of the United States and returns Florida to Spain.

19th Century

1821 Spain cedes Florida to the United States.

1825 Castillo de San Marcos renamed Fort Marion.

20th Century

1924 Fort Marion and Fort Matanzas are proclaimed national monuments.

1933 Fort Marion and Fort Matanzas are transferred from the War Department to the National Park Service.

1935 National Park Service begins exclusive administration of both national monuments.

1942 Original name—Castillo de San Marcos—is restored.

St. Augustine

Established in 1565 by Don Pedro Menéndez de Avilés, St. Augustine is the oldest permanent European settlement in the continental United States. For 235 years it was the political, military, and religious capital of the Province of Florida from which Spain exercised jurisdiction over a vast geographical region. The town's principal value, though, was a military base for the protection of Spain's colonial trade and commerce.

St. Augustine is also perhaps the earliest example of community planning within the continental United States. This is exemplified by its regular and narrow streets, a pleasant central plaza, abundant open spaces, beautiful patios and gardens, impressive government and religious buildings, and comfortable homes—all suggesting an emphasis on the development of an orderly, dignified, healthy, and pleasant environment. The character of the city still reflects its vibrant Spanish heritage.

A Guide to the Castillo

The layout that Spanish engineer Ignacio Daza created for the Castillo de San Marcos is simple and straightforward. This fortress is a hollow square with diamond-shaped bastions at each corner, with only one way in or out. In the bombproof storerooms that surround the central Plaza de Armas you will find museums highlighting various chapters of the fort's long history. A good place to start is the corner rooms next to the well. Restrooms are located under the arched stairway leading to the gundeck. After you finish exploring the rooms below, make your way up the stairs and gaze out upon the waters of Matanzas Bay. From this commanding position, a garrison of Spanish troops safeguarded St. Augustine during the turbulent colonial era. Later English and then American troops also saw service here. All stood watch faithfully over the land Juan Ponce de Leon named "La Florida."

Shot Furnace
The US Army filled in the east side of the moat in 1842-44 and mounted sea coast artillery pieces along the seawall. The shot furnace heated cannonballs until red hot. This hot shot was then fired at an enemy's wooden ships to set them afire.

Powder Magazine, 1675-87
This was the only vaulted chamber completed when the Castillo was first built. The rest were added during a later modernization. Its thick coquina walls were buried in the earth fill of San Carlos Bastion to protect the fort's gunpowder from fire or enemy shot. Lack of ventilation, however, made it too damp in the small room to store powder. When larger, better vaults were built, the powder was moved and this room was walled off.

Religion was important in Spanish daily life. In this chapel a priest conducted mass for the soldiers. With the introduction of Christianity to the American Indians in this area, various missions were established north and west of St. Augustine. The Spanish set up Florida's mission system over 100 years before they set up missions in the American West.

British Room, 1763-84
British troops moved to St. Augustine after Spain ceded Florida to Great Britain in exchange for the fortified harbor and city of La Habana, Cuba, in 1763. Wooden second floors, like the one reconstructed in this casemate, were built in the high Spanish vaults to provide more space for quarters and supplies. British rule lasted for 21 years. Florida was returned to Spain at the close of the American Revolution in 1783.

Plaza de Armas and Storage Rooms
Despite their prison-like appearance, the rooms around the Plaza de Armas, or central courtyard, were storage areas. Here the Spanish stockpiled gunpowder, ammunition, weapons, lumber, tools, and food like dried beans, rice, flour, and corn. Since St. Augustine was not self-sufficient, such stockpiles of food and ammunition were an important part of the town's defense during a siege.

Guard Rooms
St. Augustine was a garrison town or presidio, and no one lived inside the Castillo during the Spanish years. The soldiers lived in town with their families and came to the fort to stand a rotating guard duty (usually 24 hours). At such times, they slept and prepared their meals in these rooms. The large fireplaces offered warmth on chilly days and provided an area for cooking. The platforms attached to the walls served as beds for the soldiers.

This triangular outer work shielded the fort's only entrance from enemy fire. It was never finished as planned. If completed, the outer wall would have been five feet higher, with embrasures (openings) for cannon and a powder magazine. The ravel in bridge would have been secured each night at sunset; the main bridge was secured only when the fort was under attack.

Moat, Glacis, Covered Way
The Spanish kept the moat dry and, during sieges, used it as a pen for domestic animals. The moat could be filled with seawater by opening floodgates on the seawall. Around the outside of the fort is a constructed slope called a glacis. This embankment shielded and protected the lower fort walls from enemy cannon fire. The area between the glacis and the moat is called the covered (covert) way. This allowed soldiers to leave the fort and still be covered or protected by this wall.

Each of the fort's four corners is protected by a diamond-shaped bastion. Cannons in one bastion were positioned to create a deadly crossfire with those in two other bastions. The bastions' thick stone walls were packed solid with rubble and sand to support the immense weight of the cannon.

Cubo and Rosario Lines
After the British burned St. Augustine during the siege of 1702, the Spanish surrounded the town with a wall made of earth and palm logs, and a wide, shallow moat. The only entrance was from the north through the City Gate. A portion of this wall, the Cubo Line, has been reconstructed on the park grounds.

Three shallow wells in the Plaza de Armas provided water for the garrison. One of the wells still exists. Fresh water lies six to eight feet below the surface.

Hours of Operation
The park is open 8:45 am to 5 pm every day except Thanksgiving and December 25.

For a Safe Visit
Although the Castillo is over 300 years old, most of the damage has resulted not from past battles or sieges but from thousands of people each year. The fort is constructed of a sedimentary rock called coquina, which, despite its obvious strength, is very fragile and susceptible to wear. • Please do not climb on the walls or sit on the stone surfaces. Also do not climb or sit on the cannon. • Always watch your step. Be careful of irregular steps, low walls with no railings, and loose, uneven surfaces. • Supervise children closely.

Source: NPS Brochure (2017)


Castillo de San Marcos National Monument — June 5, 1942
Fort Marion National Monument — June 10, 1933 (Department of Interior)
Fort Marion National Monument — Oct. 15, 1924 (War Department)

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Brochures ◆ Site Bulletins ◆ Trading Cards expand section


A Master Plan for Castillo de San Marcos National Monument (July 1971)

Administrative History of Castillo de San Marcos National Monument and Fort Matanzas National Monument (Jere L. Krakow, July 1986)

Archeological Investigations of the San Pablo and San Pedro Bastions at Castillo de San Marcos National Monument, St. Augustine, Florida (Charles F. Lawson and John E. Cornelison, Jr., 2002)

Archeological Investigations of the San Pedro Bastions at Castillo de San Marcos National Monument, St. Augustine, Florida (Charles F. Lawson and John E. Cornelison, Jr., 2001)

Archeological Investigations of the San Pedro Bastions at Castillo de San Marcos National Monument, St. Augustine, Florida (Charles F. Lawson and John E. Cornelison, Jr., 2002)

Castillo de San Marcos: A Guide to Castillo de San Marcos National Monument: NPS Handbook #149 (1993)

Castillo de San Marcos and Fort Matanzas National Monuments, Florida: Historical Research Management Plan (Luis R. Arana, David C. Dutcher, George M. Strock and F. Ross Holland, Jr., December 1967)

Coastal Hazards & Sea-Level Rise Asset Vulnerability Assessment for Castillo de San Marcos National Monument and Fort Matanzas National Monument: Summary of Results NPS 343/186743, NPS 347/186743 (K.M. Peek, H.L. Thompson, B.R. Tormey and R.S. Young, November 2022)

Conservation and Reutilization of the Castillo de San Marcos and Fort Matanzas (Luis Rafael Arana, extract from Florida Historical Quarterly, Vol. 65 No. 1 Art. 6, 1986)

Cultural Landscape Report: Castillo de San Marcos and Fort Matanzas National Monuments (WLA Studio, February 2020)

Cultural Landscapes Inventory: Castillo de San Marcos National Monument (2020)

Excavations at the Castillo de San Marcos (1980)

Foundation Document, Castillo de San Marcos National Monument, Florida (June 2016)

Foundation Document Overview, Castillo de San Marcos National Monument, Florida (February 2017)

Historic Resource Study, The British Siege of St. Augustine in 1740: Castillo de San Marcos National Monument, Florida (Ricardo Torres-Reyes, March 10, 1972)

Historical Research Management Plan: Castillo de San Marcos and Fort Matanzas National Monuments, Florida (Luis R. Arana, David C. Dutcher, George M. Strock and F. Ross Holland, Jr., December 10, 1967)

Interpretive Plan, Castillo de San Marcos National Monument, Florida (October 1977)

Junior Ranger Activity Book, Castillo de San Marcos National Monument (2014; for reference purposes only)

"Let the Castillo be his Monument": Imperialism, Nationalism, and Indian Commemoration at the Castillo de San Marcos National Monument in St. Augustine, Florida (©Claire M. Barnewolt, Master's Thesis Virginia Commonwealth University, May 1, 2018)

Masonry Forts of the National Park Service: Special History Study (F. Ross Holland, Jr. and Russell Jones, August 1973)

Monument Historic Resource Study, Castillo de San Marcos National (Jennifer D. Brown, March 1997)

National Register of Historic Places Nomination Form

Castillo de San Marcos (Luis R. Arana, June 14, 1973 revised June 1976)

Natural Resource Condition Assessment, Castillo de San Marcos and Fort Matanzas National Monuments, Florida NPS Natural Resource Report NPS/NRPC/WRD/NRR-2012/515 (Jessica L. Dorr, David M. Palmer and Rebecca M. Schneider, April 2012)

Resumen del documento fundacional, Monumento nacional Castillo de San Marcos (February 2017)

Spanish Exploration and Settlement: The National Survey of Historic Sites and Buildings — National Historic Landmark Theme Study — Theme IV (April 1959)

The Building of Castillo de San Marcos (HTML edition) NPS Interpretive Series History No. 1 (Albert C. Manucy, 1942, reprint 1959)

The History of Castillo de San Marcos & Fort Matanzas From Contemporary Narratives and Letters NPS Source Book Series No. 3 (Albert C. Manucy, reprint 1455)

The History of Castillo de San Marcos & Fort Matanzas From Contemporary Narratives and Letters (HTML edition) NPS Source Book Series No. 3 (Albert C. Manucy, reprint 1955, 1959)

Volunteer Handbook: Castillo de San Marcos & Fort Matanzas National Monuments (July 2021)


Castillo de San Marcos National Monument

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Last Updated: 24-May-2024