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  • Writer's pictureTim Murphy

Castillo de San Marcos

Located in St. Augustine, Florida, Castillo de San Marcos is the oldest surviving example of European masonry fortifications in America. Originally constructed between 1672 and 1695, the fortress emulated the colonial authority of Spain; however, ensuing decades of conflict drastically altered the power dynamics in North America, ultimately resulting in United States sovereignty. Castillo de San Marcos—with its long and embattled history, distinguished architecture, and cultural materiality—persists today as one of America’s most influential national monuments.


The Age of Discovery dawned in the New World when Christopher Columbus charted the Caribbean Islands (mistakenly termed the “West Indies”) in October 1492. His settlement and subsequent decimation of indigenous populations opened the floodgates for European conquest. Spanish military-adventurers known as conquistadores colonized the mainlands of Central and South America, securing loads of precious metals and territory for the growing empire. In March 1513, Juan Ponce de León discovered the Floridian Peninsula—a protuberant land mass proximal to strategic trade routes in the Gulf Stream. Spanish inquisitors sought to fortify Florida’s coastline and protect their maritime interests from pugnacious European powers, but a series of costly and unsuccessful colonization attempts squandered these ambitions.

In 1564, French Huguenots (Calvinist Protestants) under Jean Ribault and René de Goulaine de Laudonnière established Fort Caroline near present-day Jacksonville, Florida. King Philip II perceived this “invasion” as a threat to Catholicism and Spanish interests in the New World and dispatched Don Pedro Menéndez de Avilés to eradicate the French colonizers. On September 8, 1565, Menéndez, along with eight hundred Spanish settlers, established the coastal town of St. Augustine—the oldest permanent European settlement in the United States. Ribault sailed south two days later to confront the Spaniards, but a hurricane wrecked his fleet near the Canaveral shoreline. While Ribault embarked on his ill-fated campaign, Menéndez simultaneously launched an overland assault against the undermanned French outpost. On September 20, five hundred Spanish soldiers stormed Fort Caroline, killing nearly 150 of its defenders. Laudonnière and a handful of others managed to escape back to France while the remaining inhabitants were taken prisoner.

Several days later, Menéndez encountered a detachment of Ribault’s men on Anastasia Island. The Spanish seized the Frenchmen and killed 111 of the 127 shipwrecked survivors. Two weeks later, the remainder of Ribault’s force was captured, resulting in the massacre of 134 men, including Ribault himself. The destruction of Fort Caroline and decisive slaughter of French settlers solidified Spain’s sole possession of the Floridian coast, although the threat of enemy raids persisted throughout the ensuing decades.

St. Augustine twice fell victim to pirate attacks—the first occurring during the unofficial Anglo-Spanish War (1585 – 1604) at the hands of Sir Francis Drake, who organized paramilitary expeditions against Spanish settlements along the Florida Straits. In May 1586, Drake descended upon St. Augustine with an attacking force of nearly two thousand men. The Spanish sortie on Anastasia Island bitterly contested the privateers, holding off their landing parties until nightfall; however, Governor Pedro Menéndez de Márquez, whose garrison was outnumbered six-to-one, decided to abandon St. Augustine and its wooden bulwark, Fort San Juan de Pinos. The Spanish withdrew into the woods overnight, leaving behind fourteen bronze cannon and two thousand gold ducats ($300,000) in their haste. Drake seized the spoils the following morning and burned Fort San Juan to the ground.

English buccaneer Robert Searles led a second raid against St. Augustine on May 28, 1668. Using a captured Spanish cargo ship, Searles sailed covertly into Matanzas Bay and attacked under cover of darkness. Sergeant Major Nicolas Ponce de León managed to evacuate 130 civilians to safety within the town’s fort, but many others were left to the mercy of Searles’ crew. Governor Francisco de la Guerra’s garrison put up stiff resistance against Searles, sustaining ten casualties while inflicting thirty. Unable to capture the fort, the pirates systematically sacked the town over the next six days. While Searles spared the town from burning, his raid left sixty Spaniards dead and dozens more wounded. Many of St. Augustine’s Black and Indigenous occupants were forcibly removed and later sold into the Jamaican slave market.

In March 1669, Mariana, Queen Regent of Spain, authorized construction for a permanent masonry fort in St. Augustine. She dispatched Florida’s newly-appointed governor, Manuel de Cendoya—a 23-year veteran of the Spanish military—to secure the necessary funds from Mexico. Cendoya arrived in St. Augustine in 1671, bringing with him military engineer Ignacio Daza, Master of Construction Lorenzo Lajones, and hundreds of skilled stonemasons from Cuba. The Spanish also conscripted convicts, Black slaves, English prisoners-of-war, and indigenous peoples to quarry coquina stone—sedimentary rock composed of ancient shell fragments—burn lime, and transport building materials to the construction site. By September 1672, over 75,000 tons of coquina had been excavated from Anastasia Island.

The official groundbreaking for Castillo de San Marcos occurred on October 2, 1672, and construction commenced the following month; however, the Castillo’s development was hampered by several prolonged work stoppages. In early 1673, a smallpox epidemic ravaged the inhabitants of St. Augustine. Cendoya and Daza both contracted the disease that March and died within days of each other. Later in 1675, a cargo ship wrecked en route to St. Augustine, which left the project devoid of sufficient provisions and building materials for months. Construction ceased again between December 1677 and August 1679 after local authorities ran out money to pay the laborers. The main block of the Castillo—which housed a chapel, storerooms, and soldier barracks—was not completed until 1686. The moat, seawall, and outer defenses were completed over the ensuing nine years.

Though partially constructed by Black laborers, Castillo de San Marcos became a safe haven for fugitive slaves escaping British North America. Escapees were offered freedom if they converted to Catholicism and pledged their allegiance to Spain. King Charles II made this practice an official Spanish policy in 1693, thereby recognizing the first free community of ex-slaves in America. The king’s decree angered many Carolinian planters who retaliated by destroying Spanish outposts throughout the 1690s.


On November 1, 1700, Charles II—the last Hapsburg King of Spain—died without a biological heir. His will designated Philip, Duke of Anjou—the grandson of King Louis XIV—as the inheritor of the Spanish throne, thereby uniting the royal families of France and Spain. However, Philip’s ascension was challenged by Holy Roman Emperor Leopold I, who claimed succession on behalf of his son, Archduke Charles of Austria. England’s Queen Anne, unsettled by the prospect of a Franco-Spanish superpower, formed a “Grand Alliance” with the United Provinces and Holy Roman Empire and formally declared war against Philip’s regime on May 15, 1702. The War of Spanish Succession (also known as Queen Anne’s War) increased territorial conflicts worldwide and is often considered the “first world war of modern times.”

When news of Queen Anne’s War reached the English colonies in August 1702, South Carolina Governor James Moore convinced the provincial assembly to fund an expedition against Spanish Florida. While Moore designated himself to personally lead the campaign, he had no prior military experience—contemporaries referred to him as an “ambitious, active, [and] aggressive high-churchman.” The South Carolina Assembly, recognizing this crucial leadership deficiency, appointed Colonel Robert Daniel as Moore’s second-in-command. On October 16, 1702, Moore departed Port Royal, South Carolina, with twelve hundred men and nine warships bound for Florida.

Spanish Governor Joseph de Zúñiga y Zérda became aware of Moore’s campaign less than two weeks after the English left port. Zúñiga—a man of over twenty years’ experience with the Spanish military—quickly organized St. Augustine’s defensive strategy. He ordered the town’s inhabitants into the fort, commandeered all food stores, and dispatched messengers to Spanish strongholds in Pensacola, Havana, and Mobile for reinforcements. Nearly 1,600 Spanish civilians and soldiers quartered inside the Castillo with enough provisions to last several months.

Around midnight on November 3, Moore’s forces stormed Amelia Island, sacking Spanish missions in succession for two straight days. Before Moore’s fleet returned to sea, Colonel Daniel led a small force along the St. Johns River. They sacked another Spanish mission, San Diego de Salamatoto, and marched overland towards St. Augustine. Meanwhile, the English fleet entered Matanzas Bay on November 8, blockading St. Augustine’s harbor.

On November 10, the English rowed ashore and burned the Nombre de Dios mission a few hundred yards away from Castillo de San Marcos. During this attack, Spanish patrols stampeded 163 head of cattle through Moore’s lines, disrupting their advance. The Carolinians entrenched themselves around the Spanish garrison and delivered aggressive artillery fire for several hours; however, the English guns had little effect against the coquina stone walls, which absorbed the cannonballs’ impact instead of shattering, Although the Spaniards were well-protected, they did sustain several casualties when a sixteen-pound cannon exploded on their gundeck, killing three men and wounding five others.

Unable to immediately seize the Castillo, Moore prepared for a siege. The belligerents stood in tense opposition for fifty days until Spanish reinforcements—two hundred infantry and four men-of-war commanded by General Estevan de Berroa—arrived off the coast on December 29. Facing an untenable position, Moore abandoned the campaign. The English burned St. Augustine and their ships before retreating overland to the St. Johns River. The failed military expedition ruined Moore’s reputation and later forced his resignation from the governorship in March 1703.


The War of Spanish Succession ended in April 1713 with the Peace of Utrecht, which confirmed Philip V as King of Spain and simultaneously removed him from the French line of succession, thereby preserving Europe’s delicate balance of power. Britain gained the strategic Mediterranean ports of Gibraltar and Minorca and received a thirty-year Asiento de Negros—a negotiated monopoly of the African slave trade in the Spanish West Indies. The South Sea Company obtained exclusive rights to this contract, although other British merchants staked extralegal profits by smuggling black market goods into the Spanish Main. In 1729, Great Britain permitted the Spanish guarda-costa to board merchant vessels and search their cargos for contraband; however, this policy failed to curb rumrunning and essentially empowered Spanish privateers to routinely raid British ships—seizing valuables and imprisoning crews—which imbued anti-Spanish sentiments.

One particularly gruesome incident became the eponymic catalyst for a global naval conflict. In April 1731, the Spanish sloop La Isabela intercepted the Rebecca—a British merchant vessel suspected of trade violations. The Spaniards, led by Captain Juan de León Fandiño, ransacked the ship in search of contraband and valuables. When the Rebecca’s captain, Robert Jenkins, attempted to intervene, he was restrained and tortured by Spanish coastguardsmen. The captain’s maiming culminated when Fandiño "took hold of [Jenkins’] left Ear and with his Cutlass slit it down" and purportedly exclaimed “go, and tell your King that I will do the same if he dares to do the same.”

Jenkins returned to Great Britain later that June and expressed his grievances to Thomas Pelham-Holles, the Duke of Newcastle and Secretary of State for the Southern Department. However, little became of the encounter until March 1738 when Jenkins delivered his deposition before the British House of Commons. In a macabre display of theatrical vehemence, the captain exhibited his severed ear to members of Parliament, attesting to Spain’s barbaric atrocity. Jenkins’ Ear subsequently became a rallying cry for warmongering tendencies against Spain.

The Duke of Newcastle petitioned his Spanish counterparts to negotiate a new treaty that would specify proper maritime conduct and appraise financial damages incurred by each nation’s antagonism. In January 1739, mediators tentatively approved the Convention of Pardo, which stipulated that the Spanish government owed Britain £95,000 for illicit damages and confiscated property. Reciprocally, the South Sea Company was indebted £68,000 for fraudulent trade and nonpayment of Spanish taxes per the Asiento de Negros. When the Convention was introduced to Parliament, it was met with staunch opposition. The South Sea Company vigorously denied any wrongdoing and refused to pay reparations. Mutual resentment continued to mount until Britain formally declared war on October 23, 1739.

The borderlands between Spanish Florida and the British colony of Georgia erupted with hostilities during the War of Jenkins’ Ear. In early 1740, General James Oglethorpe launched a series of antagonistic military campaigns against Spanish outposts in northern Florida, destroying Forts Picolata and San Francisco de Pupo before setting his sights on Castillo de San Marcos. On June 13, Oglethorpe surrounded St. Augustine with seven warships and over two thousand combined colonial militia and Native combatants. The British expected a quick surrender, but Spanish Governor Manuel de Montiano, having anticipated the assault, reinforced the Castillo with an additional six hundred troops and two months of provisions earlier that April. After eleven days of tense standoff, Oglethorpe launched a sustained, 27-day artillery bombardment against the fortress, hoping to pummel the Spaniards into capitulation. However—much like Governor Moore’s failed Siege of 1702—the British guns were largely ineffective against the Castillo’s coquina walls. As one Englishman observed, “[the native rock] will not splinter but will give way to cannon ball as though you stick a knife in cheese.”

On June 26, the British suffered a demoralizing defeat at nearby Fort Mose—a partially-demolished presidio that had been captured by Colonel John Palmer immediately preceding the siege. Palmer’s company was ambushed in a predawn, surprise attack by three hundred Spanish regulars, Seminole warriors, and free Black auxiliaries under Captains Antonio Salgado and Francisco Menéndez. Brutal hand-to-hand ensued for nearly an hour before overwhelmed British forces evacuated the fort. Of Palmer’s 143-man command, more than half were killed or captured, including Palmer himself.

Shortly after “Bloody Mose,” Acting Commodore Vincent Pearce withdrew his naval squadron from Matanzas Bay due to heavy rains and the possibility of an approaching gale. The Royal Navy’s departure provided an unprecedented opportunity for Spanish sloops in Cuba to resupply the Castillo. The navy’s failure to enforce the blockade was soon followed by its complete abandonment. The advent of hurricane season persuaded the cautious Pearce to permanently retire to port. Oglethorpe—facing a freshly-reprovisioned Spanish garrison without any naval support—decided to abandon the siege on July 20. Oglethorpe’s failed campaign resulted in more than 150 British casualties. Spanish forces reportedly lost less than a dozen men.


Following the Seven Years’ War, Spain ceded Florida to Great Britain in exchange for Cuba and the Philippines, per the Treaty of Paris (1763). The Florida Territory was subsequently divided into East and West sections, becoming the 14th and 15th British colonies in North America. St. Augustine remained the capitol of East Florida and Castillo de San Marcos was renamed Fort St. Mark.

St. Augustine emerged as a lively Loyalist stronghold during the American Revolutionary War. Fort St. Mark quartered British troops, stored military supplies, and even served as a prisoner-of-war camp. Christopher Gadsden, the Lieutenant Governor of South Carolina, was arguably the most famous individual incarcerated at Fort St. Mark. On May 12, 1780, Gadsden surrendered the city of Charleston to British forces following a six-week siege that completely quashed the Continental Army’s Southern Department. While British General Sir Henry Clinton initially paroled members of the civil government, Lieutenant General Charles Cornwallis rescinded this decision three months later. On August 27, Gadsden and twenty of his colleagues were arrested and transported to St. Augustine, where East Florida Governor Patrick Tonyn offered them freedom of the town in exchange for parole. All the detainees conceded except for an indignant Gadsden, who replied, “I gave my parole once, and it has been shamefully violated by the British Government. I shall not give another to people on whom no faith can be reposed.” For his defiance, Gadsden spent 42 weeks in solitary confinement. He was released in July 1781 during a prisoner exchange.


Great Britain had little desire to maintain possession of Florida after unsuccessfully contending the American Revolution. On July 12, 1784—in accordance with the Peace of Paris (1783)—British authorities relinquished Florida back to Spain; however, newly-sovereign Americans living along the territory’s northern border were anxious to expel the Spaniards in the interest of expansionism. During the summer of 1795, a group of American settlers—presenting themselves as French revolutionaries—staged a revolt against the Spanish known as “Florida’s French Revolution.” The insurgents attacked the Spanish Battery San Nicolas (located in present-day Jacksonville), killing three soldiers and capturing the entire garrison. Although the assailants were quickly dispelled, Spanish officials tracked down three dozen suspected sympathizers and had them imprisoned at Castillo de San Marcos. Many of the accused were sentenced to death or ten-years’ hard labor; however, these punishments were never carried out and those implicated were ultimately released.

In 1812, warmongering Americans organized another insurrection against Spanish Florida known as the Patriot War. The Patriots—East Florida insurgents consisting of Spanish defectors and filibusters from Georgia and Tennessee—wanted to declare their independence from Spain and assimilate with the United States. American officials, motivated by Florida’s strategic commercial potential, surreptitiously supported the prospective annexation. On January 15, 1811, Congress secretly passed “An Act to enable the President of the United States, under certain contingencies, to take possession of the country lying east of the river Perdido, and south of the state of Georgia and the Mississippi territory, and for other purposes”—a long-winded piece of legislation that authorized then-President James Madison to occupy Florida with military force, pursuant to the consent of local authorities or invasion of foreign powers. General George Mathews (former governor of Georgia) and Colonel John McKee were appointed to enact the legislation by “fomenting unrest” with Florida’s populace, though their instructions were not so explicitly directed.

Mathews corresponded with Patriot leader John Houston McIntosh and assured the support of the United States military in his group’s endeavors. In March 1812, the Patriots, protected by American gunboats, marched threateningly towards St. Augustine, usurping the Spanish port of Fernandina and its neighboring settlements. At the time, Castillo de San Marcos was manned by four hundred soldiers—mostly free Blacks and Indian allies—as the majority of Spain’s regular troops were resisting French occupation at home. Despite the reduced manpower, Patriot forces found the city’s defenses impregnable. One soldier recalled, “[our] aim is at Fort St. Augustine; five times the force we have will not be able to take it by storm, it’s the best and most secure fortified fort I have seen.” The rebels moved north and captured Fort Mose. Federal troops—the First Regiment of U.S. Riflemen under Lieutenant Colonel Thomas A. Smith—arrived later that April; however, a harassing bombardment from a Spanish flotilla compelled their withdrawal just a few weeks later. Spain and her Native allies continued to raid Patriot positions throughout the summer.

In June 1812, as war with Great Britain grew increasingly imminent, the federal government silently withdrew its support for the Patriot cause. The ambition to capture St. Augustine was ultimately lost on September 12, 1812, when an American shipping convoy was ambushed in nearby Twelve Mile Swamp, resulting numerous casualties, including the deaths of several U.S. Marines.


In February 1819, Spanish and American representatives negotiated the Adams-Onís Treaty, which ceded Florida to the United States for $5 million. The agreement, however, was not formally ratified by the Spanish government until January 29, 1821, and the transfer of proprietary jurisdiction remained incomplete until July 10. In January 1825, the Castillo was renamed Fort Marion to honor General Francis Marion, an American Revolutionary War hero nicknamed “The Swamp Fox.”

Fort Marion was in markedly poor condition at the time of American occupation. Years of neglect had deteriorated the fort’s structural integrity to uninhabitability. This, combined with its outdated bastioned framework, rendered Fort Marion nonessential to the national defense, according to War Department officials.

The acquisition of Florida stimulated American settlement, which escalated tensions with the remaining Native American populations, specifically the Seminole Nation. White settlers placed increasing pressure on the federal government to intervene in the name of Manifest Destiny. In 1830, President Andrew Jackson passed the Indian Removal Act, which endorsed the forced removal of Native Americans from their homelands to Oklahoma reservations, sparking the Trail of Tears. The Seminoles violently resisted this sanction, igniting the Second Seminole War (1835 – 42), one of the deadliest American Indian wars ever fought on U.S. soil.

In October 1837, Seminole Chief Osceola was deceptively detained at Fort Peyton while attending a supposed peace conference with American officials. He, along with several of his followers—including Uchee Billy, King Philip, and Coacoochee (Wild Cat)—were imprisoned at Fort Marion where they endured inhumane living conditions, physical abuse, and psychological torture. On November 19, Wild Cat and nineteen other Native prisoners successfully escaped captivity. Their mistreatment at Fort Marion fueled Wild Cat’s desire to continue fighting, prolonging the war for nearly five additional years.

On January 10, 1861, the Florida State Legislature voted unanimously for secession, making it the third southern state to break away from the Union. Three days before Florida officially seceded, 125 Florida militiamen descended upon Fort Marion to secure its cannons and munition stores. Ordinance Sergeant Henry Douglas—the solitary Federal presence in St. Augustine—demanded the southerners sign a receipt for the fort and its contents. Only then did he give up the keys.

Confederate troops dismantled Fort Marion’s guns and shipped them to more strategic defensive positions across the South. A local militia unit, the Saint Augustine Blues, was enrolled into the Confederate Army on the fort green August 5, 1861. Two companies from the 3rd Florida Infantry (roughly 70 men) maintained the Confederate presence in St. Augustine until February 1862, when 26 U.S. Navy ships anchored off the inlet. Facing a much superior Union force, the Confederates deserted St. Augustine, leaving the city open to peaceful occupation. Between 1863 and 1865, Fort Marion operated as a convalescent camp and restorative health hospital for recovering Union soldiers. During the Reconstruction Era, Fort Marion became the Florida Headquarters for the United States Army.

In May 1875, military officials incarcerated 72 Plains and Apache Indians at Fort Marion. Under the supervision of Captain Richard Henry Pratt, the captives were enrolled in scholastic and vocational programs to augment their assimilation into Western society. Captain Pratt introduced penal reforms and artistic pursuits that encouraged autonomy and self-expression—educational modalities that embodied the core ideals of Pratt’s Carlisle Indian Training School, founded in 1879. The prisoners at Fort Marion were released to the Indian Bureau in 1878, with some individuals continuing their education at the Hampton Institute in Virginia. In April 1886, five hundred Apache prisoners arrived at Fort Marion and received similar indoctrination.

During the Spanish-American War, Fort Marion was utilized as a supply depot and military prison for deserters before being decommissioned in 1900. In 1924, President Calvin Coolidge recognized the fort as a national monument. In 1933, Castillo de San Marcos was transferred from the War Department to the National Park Service; however it was temporarily reactivated by the Coast Guard during World War II. Today, Castillo de San Marcos is the only extant 17th century masonry fortress in the United States and a prime example of "bastion system" engineering.

The National Park Service offers a self-guided tour of Castillo de San Marcos and its premises. Beginning at the Sally Port, visitors can marvel at the thickness of the Castillo’s fourteen-foot, exterior walls and move through the old guard quarters. Once inside the fort, take a moment to enter the rooms on the courtyard’s periphery. These chambers contain several exhibits detailing the Castillo’s construction, Florida’s cultural history, contemporary weapons and artillery implements, and Indigenous influences. The Castillo’s upper level features the gun deck with over sixty cannon variations on display.

Outside, visitors can walk around the dry moat and see several other Castillo structures. The Ravelin—an unfinished triangular bastion positioned before the south wall—shielded the entrance from enemy fire. On the east side stands the Water Battery (seawall cannon placements constructed by the U.S. Army Corps of Engineers in 1842) and Hot Shot Furnace, which cooked cannonballs red-hot to fire onto wooden ships and cause incendiary damage. A replica of the Cubo Line—a fortified wall that stretched around St. Augustine—can be viewed from the northwest aspect of the fort.

Castillo de San Marcos possesses one of the most diverse and captivating histories in America. It has witnessed the rise and fall of empires, withstood several siege attempts, and manipulated the dichotomous relationship between freedom and subjugation. The Castillo’s 17th century stonework and supporting architecture are exceptional rarities in the Western Hemisphere, upholding an ideal environment for historical immersion.

For more information on the history of Castillo de San Marcos, visit the National Park Service, Only in Your State, Legends of America, National Park Planner, Georgia History, St. George Inn, and LibCom

Check out the following publications for more history:

  1. Baine, Rodney E. “General James Oglethorpe and the Expedition Against St. Augustine.” The Georgia Historical Quarterly 84, no. 2 (2000): 197–229.

  2. Covington, James W. “Drake Destroys St. Augustine: 1586.” The Florida Historical Quarterly 44, no. 1/2 (1965): 81–93.

  3. Herson Jr., James P. "A Joint Opportunity Gone Awry: The 1740 Siege of St. Augustine." School of Advanced Military Studies, United States Army Command and General Staff (1997).

  4. Mauncy, Albert C. "The History of Castillo de San Marcos & Fort Matanzas: From Contemporary Letters and Narratives." U. S. Department of the Interior, National Park Service (1943).

  5. Reigelsperger, Diana. “Pirate, Priest, and Slave: Spanish Florida in the 1668 Searles Raid.” The Florida Historical Quarterly 92, no. 3 (2014): 577–590.


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