Florida’s Unconquerable Fort Has Protected This Beautiful Peninsula for 300+ Years

Castillo de San Marcos, St. Augustine FL

The oldest stone fortress in America sits quietly in St. Augustine, watching ships pass by just like it did 327 years ago. Spanish soldiers once walked these walls, defending their empire’s northern edge.

Wars came and went but the castle stayed. Here’s how this tough old fort did it.

Built for the Spanish

The oldest stone fort in the continental United States stands on the shore of Matanzas Bay in St. Augustine, Florida. Construction began in 1672 and took 23 years, finishing in 1695.

Spanish engineer Ignacio Daza designed this massive stone fortress to protect Spain’s claims in the New World. The star-shaped structure covers 20.5 acres of prime waterfront.

Why Coquina Stone Made This Fort Impenetrable

Spanish builders used a special material called coquina to build Castillo de San Marcos. This light limestone forms when tiny shell pieces stick together over hundreds of years.

The fort’s walls were 14 feet thick at the bottom and 9 feet thick at the top. When cannonballs hit these walls, they just sank into the soft coquina instead of breaking through.

This made Castillo de San Marcos almost impossible to destroy with old-time weapons.

How Smart Design Protected Against Attacks

Italian builders created the “bastion system” in the 1400s to fight off cannon attacks. Four diamond-shaped corners called San Pedro, San Agustín, San Carlos, and San Pablo stuck out from the main fort, letting Spanish soldiers shoot at enemies from different angles.

The walls started at 22 feet tall but were made taller during repairs from 1738 to 1756. A triangle-shaped wall protected the entrance while a dry ditch went around the fort.

Builders made gentle slopes on the land sides, forcing attackers to run uphill while getting shot at from above.

How Governor Moore Failed To Take The Fort In 1702

South Carolina Governor James Moore attacked first in 1702 during Queen Anne’s War. His forces surrounded the fort for exactly 58 days from November to December.

About 1,500 people packed inside during the attack. Moore put cannons in town buildings, but the English cannonballs just got stuck in the soft stone walls without doing damage.

After two months of trying to break through, Moore burned down St. Augustine before giving up. Spanish help from Havana made him leave even faster.

Oglethorpe’s Failed 27-Day Attack In 1740

Georgia Governor James Oglethorpe tried again in 1740 during the War of Jenkins’ Ear. He brought British soldiers, local fighters, and Native American allies to attack the fort.

About 300 soldiers and 1,300 townspeople hid inside while Oglethorpe shot at the walls for 27 days. Like Moore, he found out cannonballs couldn’t hurt the stone.

His forces blocked the water entrance to starve the city, but some Spanish supply ships got through. Running low on food and hope, Oglethorpe gave up without taking the fort.

When Five Different Countries Owned The Fort

Spain controlled the fort twice: 1695-1763 and 1783-1821, keeping the name Castillo de San Marcos. Britain took over in 1763 through a peace treaty, calling it Fort St. Mark until 1783.

The United States got Florida through a deal in 1819. American troops took control in 1821, renaming it Fort Marion after a Revolutionary War hero named Francis Marion.

Confederate soldiers briefly held the fort in 1861 before Union troops took it back. Congress brought back the original Spanish name in 1942.

Amazing Seminole Escape From Fort Marion

American forces tricked and captured Seminole leader Osceola in October 1837 during the Second Seminole War. They locked him up at Fort Marion with other leaders including Uchee Billy, King Philip, and Coacoochee.

On November 19, 1837, Coacoochee and nineteen other Seminoles broke out. Coacoochee said he and Talmus Hadjo squeezed through an 8-inch window and slid down a rope into the empty ditch.

The escapees kept fighting for four more years. Osceola was moved to another fort, where he died on January 30, 1838.

America’s First Prison For Western Native Tribes

Fort Marion held Native Americans prisoner during three different times in the 1800s. In 1875, the Army brought 72 men from Plains tribes including Kiowa, Cheyenne, Arapaho, Comanche, and Caddo peoples.

Lieutenant Richard Henry Pratt ran a three-year program to change their culture through English lessons, Christianity, and military training. During this time, Plains Indians created Ledger Art using whatever materials they could find.

In 1886, over 500 Apache prisoners including Geronimo’s family arrived. The fort was built for 150 people but became dangerously crowded with Apache families living in tents on the roof.

The British Prison For American Patriots

British forces used the fort as a military prison during the Revolutionary War after taking control on July 21, 1763. They added second floors to fit more people.

Christopher Gadsden, South Carolina’s second-in-command governor and Declaration of Independence signer, spent 11 months locked up here. Though tour guides mention three signers were held, history books only prove Gadsden was imprisoned.

Conditions were terrible with small spaces and little food. A peace treaty in 1783 gave Florida back to Spain, ending British control of the prison.

How Enslaved People Built This Fort

Construction officially started October 2, 1672, when workers laid the first stone blocks. Spanish leaders used enslaved Africans, Native Americans from nearby tribes, and Cuban prisoners. Skilled builders from Havana supervised the work.

Later, this fort built by enslaved people became an escape route to freedom. Spanish leaders freed runaway slaves from British colonies if they became Catholic, a rule made official in 1693.

This led to Fort Mose being built in 1738, America’s first legal free Black community.

The Fort’s Role In The Civil Rights Movement

In 1964, the fort’s grounds became a meeting place for civil rights protesters. A big tree called the “Freedom Tree” was a gathering spot on federal land, where demonstrations could legally happen despite local bans.

Leaders including Dr. Robert Hayling, Hosea Williams, and Dr. Martin Luther King Jr. organized protests in St. Augustine. These demonstrations faced violent opposition but got national attention about racial unfairness.

The protests helped pass the Civil Rights Act of 1964. The fort was added to the National Register of Historic Places in 1966.

Visiting Castillo de San Marcos

Today, visitors can explore this remarkable fortress at 1 South Castillo Drive in St. Augustine, Florida. The fort welcomes guests daily from 9:00 a.m. to 5:00 p.m., though it closes on Thanksgiving and Christmas Day.

Admission costs $15.00 for adults age 16 and older, while children 15 and under enter free. Each ticket remains valid for seven consecutive days.

Don’t miss the weekend cannon firing demonstrations. These happen five times daily on Saturdays and Sundays at 10:30 a.m., 11:30 a.m., 1:30 p.m., 2:30 p.m., and 3:30 p.m. Park rangers in period costumes explain historical weapons and fire the cannons.

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