In an effort to safeguard Spanish interests in the New World, King Phillip II commissioned Pedro Menendez de Aviles to dislodge the French from Florida and colonize the area for Spain.
Menendez arrived in Florida in 1565, first at what is now Cape Canaveral before traveling north to the sheltered harbor in the land he named Presidio de San Augustine.
Preparation for the construction of Castillo de San Marcos began in 1671 under the guidance of Ignacio Daza, a seasoned military engineer, and Lorenzo Lajones, a master of construction. Although Daza died seven months later the work continued according to his plan.
On Oct. 2, 1672, Governor Manuel de Cendoya and other royal officials broke ground for the fort’s foundation trench and several weeks later the first stone was laid. The site was the location of six previous wooden forts. Local Indians, slaves, freedmen, convicts and, occasionally, Spanish soldiers labored alongside skilled workers imported from Cuba.
The stone chosen for the Castillo’s walls was a local stone called “coquina,” meaning “little shells,” a type of limestone formed millions of years ago when ocean covered Florida. The weight of the water cemented little shells together. Coquina was easy to cut when wet but became hard when dry. It was quarried from Anastasia Island across the bay from the Castillo and ferried to the construction site.
In a work area that today is the Castillo’s parking lot stonemasons produced blocks. The mortar to bind the blocks to each other was made on the construction site by baking oyster shells in kilns until they were reduced to a fine white powder called lime. The lime was then mixed with sand and fresh water to produce the mortar that still holds the Castillo together today. Some 100 to 150 men worked on the fort at the time. After 23 years, the fort was finally completed in 1695.
The Castillo played an important role as a strategic military post in the New World and many flags have flown during her illustrious career. These include the Spanish (1695-1763), British (1763-1784), Spanish again (1784-1821), United States (1821-1861), the Confederate States of America (1861-March of 1862) and finally the United States of America again (1862-1900).
Changes in occupation of the fort came about through military agreement or political treaty. The Castillo was never taken by force.
The fort was built according to the bastion design system that emerged out of the medieval castle form. Engineers lowered castle walls and placed mounds of earth in front of them, establishing ramparts capable of withstanding cannon bombardment. Moats continued to be an essential component of the defense, preventing enemy forces from scaling the sloped embankments and penetrating the fort. The round castle tower matured into the angular bastion that provided protection to contiguous walls.
Bastioned forts were centered on a plaza around which immense ramparts stood. The inside of the ramparts sloped upward toward the fighting platform called the terreplein. The banquette, or firing step, rose above the terreplein and was protected by the parapet. On the exterior of the rampart, facing the moat, a masonry scarp retained the earthen rampart wall.
On the opposite side of the moat was the counterscarp above which stood the covered way. A palisade shielded the banquette for the covered way. The glacis, an earthen bank free of foliage, sloped downward from the covered way into the open country.
Seventeenth-century forts were almost always square-shaped, the linear curtain walls extended outward at the corners into diamond-shaped bastions. Ravelins, similarly shaped defensive structures, were often constructed in front of curtain walls to provide further support to the bastion points that were most susceptible to attack. Outer defense works like counterguards and hornworks, built of earth and wood and positioned in front of the fort’s main body, gave additional strength to the fort.
As a total defensive fortification, bastioned forts and their outer defenses gave a great deal of confidence to its residents during a siege. As a strategic deterrent, this super-fort did everything that was asked of her.
The fort defended the primary trade route to Europe and the Bahama Channel (as the Gulf Stream was then known) and it also served as Florida’s territorial capitol, defending against the encroachment into the northern reaches of the Spanish Empire.
Castillo de San Marcos National Monument comprises roughly 20.5 acres. The park is north of St. Augustine’s central plaza and fronts Mantanzas Bay. The city itself lies on the eastern coastal plain of Florida. It is a low-lying, sandy area protected from the sea by a number of barrier islands.
The San Sebastian River runs west of the city and formed a natural barrier for the colony early in its history. A sea wall and water battery separate the Castillo from waters of Mantanzas Bay on the fort’s east side.
The site of Castillo is a rolling, grassy area sprinkled with a few trees. The outer portions of the grounds are flat up to the glacis, which slopes upward towards the fort and roughly follows the contour of the moat and covered way. The park is irregular in shape with much of its western boundary following the contour of State Road A1A. The defense work runs west from the glacis to the City Gate, interrupted by Route A1A just east of the gate.
The Castillo is built around a square plaza whose sides are 230 feet long and has diamond-shaped bastions named for four Roman Catholic saints, San Augustine, San Pablo, San Pedro and San Carlos, protruding to each corner. Visitors enter over the drawbridge.
The coquina walls are 30 feet high, 10- to 14-feet thick at the base and 5-feet thick at the top. Originally three cisterns provided fresh water. Today there is only one.
Vaulted casements support the wide terreplein and embrasures are situated strategically along the top of the wall. Just next to the entrance room were the guard rooms. Directly across the plaza from the entrance was the chapel.
The garrison had a nominal strength of 350 men although that number fluctuated slightly. Deaths from yellow fever and other tropical diseases were fairly common. In addition, rosters were sometimes inflated when deceased soldiers were surreptitiously kept on duty lists so spouses could collect benefits and pay.
Cannon were of assorted sizes and calibers, contingent on the type of ground that had to be defended. The biggest guns were on the waterfront while the smaller calibers were consigned to the land sector that was afforded additional protection by existing rough ground.
Prior to the Castillo’s completion cannon were placed only in the bastions. San Augustine (southeast bastion) protected the harbor and its entrance and also St. Augustine proper. San Pablo (northwestern bastion) guarded the land approach to the fort and the town gate. San Pedro (southwestern bastion) was inside the town limits. Its guns acted as a reserve for San Pablo. San Carlos (northeastern bastion) guarded the harbor and marshland to the north.
In 1683 the Castillo was armed with 29 guns: an iron 2-pdr., bronze 3-pdr., two 4-pdrs. (iron and bronze), five 5-pdrs. (four iron, one bronze), five 7-pdrs. (four iron, one bronze), a bronze 8-pdr., three iron 9-pdrs., two 10-pdrs. (iron and bronze), two 12-pdrs. (iron and bronze), three iron 16-pdrs., one bronze 18-pdr., a bronze 40-pdr., and an iron stone mortar. Additionally there were nearly 12 unmounted pieces, some unserviceable.
The bastion San Augustine was formidably armed with a 40-pdr., 18-pdr., two 16-pdrs., two 12-pdrs., an 8-pdr., 7-pdr., 4-pdr., and 3-pdr. Bastion San Pablo defended itself with one 16-pdr. demi-cannon, a 10-pdr. demi-culverin, two 9-pdrs., one 7-pdr. demi-culverin, a 7-pdr. and a 5-pdr.
Bastion San Pedro was protected by one 9-pdr., two 7-pdrs., two 5-pdrs. and a 4-pdr. Bastion San Carlos had a 10-pdr., two 5 pdrs. and one 2-pdr.
Although the bronze guns were named to signify their operational characteristics the names also had metaphorical meanings — 2- and 4-pdrs. were called falcons; 6-pdrs. were sakers (from the saker hawk); 8-, 10- and 12-pdrs. were demi-culverin (from the Latin colubra meaning snake); 15-, 18-, 20- and 22-pdrs. were called culverins; 12-pdrs. were third- or demi-cannon; 20- and 25-pdrs. were known as demi-cannon; while 30-, 35-, 40-, 45- and 50-pdrs. were called simply cannon, although the 40-pdrs. were also known as double culverins or dragons. Culverins were the only guns capable of reaching the harbor sandbar 3,000 yards away.
By 1706 the Castillo’s armament had increased to 35 guns with the addition of six iron pieces ranging from 4- to 10-pdrs. In 1740 the number of guns almost doubled to 65. Added were two iron and two bronze 3-pdrs., four iron 4-pdrs., nine iron 5-pdrs., five 6-pdrs., 11 8-pdrs., six 15-pdrs., four 18-pdrs., a 24-pdr. and a 33-pdr.
The greatest number of guns the Castillo ever manned was 77 in 1763 when 10 bronze 8-pdrs., five iron 10-pdrs., 12 iron 12-pdrs., a bronze 16-pdr., seven iron 18-pdrs., seven iron 24-pdrs., a bronze 36-pdr., and 18 small mortars were added. In 1765 the total number of guns decreased to 63, in 1812 it was almost halved to 34 and in 1834 armament was reduced to 20 guns.
The most effective assault of the Castillo ensued during the siege of 1740 in which round shot did the most damage. The heaviest British siege cannon were 18-pdrs. situated over 1,000 yards from the fort. Spanish Engineer Pedro Ruiz de Olano recounted that the balls did not puncture the main walls more than a foot and a half, but the parapets, being only three feet thick, suffered significant damage.
Today there are 27 pieces inside the fort and 11 outside. Because the different occupiers of the fort brought many of their own guns to add to the ordnance that had been left behind the collection of guns is large and eclectic.
The original pieces include an iron 18-pdr. with a range of 3.3 miles, a 24-pdr. of 3.8-mile range and two 2-pdrs.
The fort’s east side moat was filled in 1842 to create a water battery with guns facing the harbor. The water level could be controlled by gates in the reinforced sea wall and, if needed, the moat could be drained and livestock kept in the moat to feed people inside the fort during an attack.
A stuccoed, coquina hot shot furnace was built in 1844 on top of the water battery. It is 9 feet long and 11 feet wide with a chimney 11 feet high.
The construction of the seawall, water battery and hot shot furnace was an attempt to update the Castillo and make it a contributing part of the 19th-century coastal defense system as a result of the Second Seminole War and national attempts to prepare the coastline in the event of naval attack.
They illustrate the military thinking at the time and demonstrate the development of military engineering and technology. They also were the last construction projects at the fort.
As a provision of the Treaty of Paris that ended the Seven Years War Britain gained possession of Florida (and the Castillo) in 1763 and changed its name to Fort St. Marks. During the American Revolution the fort held patriots captured by the British.
In the treaty settlement at the end of the American Revolution Spanish troops returned to St. Augustine in July 1784 and changed the name back to the Castillo de San Marcos. However on July 20, 1821, Spain ceded Florida to the U.S.
On their arrival in St. Augustine, the Americans changed the name to Fort Marion in honor of General Francis Marion, the Revolutionary War hero known as the “Swamp Fox.” The old storeroom was converted into prison cells during the American Territorial Period and the fort served briefly as a prison for captured Seminole warriors, among them Osceola.
Fort Marion was in Union hands for the majority of the Civil War. The fort was handed over to the Confederates in January 1861 but came back into the Union hands on March 11, 1862, when the USS Wabash, a Union gunboat, took the city and the fort without firing a shot after realizing that Confederate forces had evacuated the area.
During the 1870s and 1880s Kiowa, Comanche, Cheyenne, Caddo, Arapaho and Apache Indians captured in the West were imprisoned at the fort. On May 21, 1875, 71 Indians escorted by Lt. Richard H. Pratt arrived at the fort. Pratt’s experience with them led him to establish the Carlisle, Pa., Indian Training School in 1880.
The Castillo resumed its role as a prison during the Spanish-American War in 1898, holding nearly 200 court-martialed American deserters. After the war the fort was decommissioned. In 1924 President Calvin Coolidge, acting under the authority of the Antiquities Act of 1906, declared Fort Marion to be a National Monument.
The fort was transferred from the War Department to the National Park Service, U.S. Department of the Interior, in 1933. The original name, Castillo de San Marcos, was restored to the installation in 1942. With the passage of the National Historic Preservation Act Castillo de San Marcos National Monument was placed on the National Register of Historic Places in 1966.
Castillo de San Marcos is at 1 Castillo Dr. in St. Augustine. Its phone number is (904) 829-5606. The fort is open from 8:45 to 5:15 every day except Christmas. Admission is adults $5, children 6-16 $2. No pets are allowed.
Everything except the gun deck is handicapped accessible. Tours are given in English and Spanish. The park rangers are friendly and extremely knowledgeable about the guns.
(About the Author: Michael Garlock is a freelance writer who previously wrote about Forts Jefferson, Zachary Taylor and Wadsworth. )