Fort Jefferson

Fort Jefferson is a huge coastal masonry fort on Garden Key, the main historic attraction in Dry Tortugas National Park. It was built to protect a deepwater harbor and shipping lanes between the Gulf of Mexico and the Straits of Florida. Its red-brick arcades enclose a broad grassy parade ground, with the shallow blue-green water of the moat and surrounding sea just beyond the walls. If the fort’s history is your reason for coming, make it your first stop; swimming and snorkeling are separate activities around the shore.

There’s no road to Garden Key: visitors arrive by ferry or seaplane from Key West, or by private vessel. Ferry reservations can sell out months ahead, so book transportation early. There’s no restaurant or shop for supplies on the island; check whether your boat serves food and bring what you’ll need ashore. The Garden Key Visitor Center is just inside the fort entrance, to the right, with exhibits, a short film, ranger information and a bookstore. The visitor center is wheelchair accessible, but that doesn’t mean every uneven passage or rampart is accessible.

The fort’s scale makes more sense on foot. Two tiers of arches run along the inner walls, framing the parade ground; thick masonry holds rooms and passages that shift from open daylight to shadow. Outside, the walls look out over the moat and the clear, shallow water around Garden Key. Visitors often combine the fort with time on the shore, but the boat’s schedule sets the limits of the island visit.

Construction began in 1846 and continued until 1875, but the fort was never completed or fully armed. It was designed as part of the country’s coastal defenses, guarding an unusually strategic deepwater harbor where ships could shelter, resupply or refit along major Gulf and Florida shipping routes. The fort was never attacked. During the Civil War, Union warships used the harbor in the blockade of Southern shipping.

Fort Jefferson also served mainly as a federal prison for Union deserters and other military convicts. Its best-known prisoner was Dr. Samuel Mudd, who arrived in July 1865 with three other men convicted in the Lincoln assassination conspiracy. He spent most of his sentence on the second tier above the sallyport. After yellow fever killed the chief surgeon and four nurses, Mudd helped treat victims at the fort; President Andrew Johnson pardoned him in 1869. The room associated with him is known as Dr. Mudd’s Cell.

The name can make the Fort Jefferson Dungeon sound like an underground pit, but there are no underground dungeons here. The so-called dungeon was a lower-level room in Bastion D used to punish prisoners. Mudd spent time there after an escape attempt, and the fort’s other notorious prisoner, George St. Leger Grenfel, was also sent there.

The Army abandoned the fort in 1874. It later served as a coaling station for warships; in 1898 the USS Maine sailed from the Tortugas toward Havana. The fort also saw brief military use during both world wars, long after its original coastal-defense role had ended.

From the entrance bridge, line up the pale doorway with the red-brick wall and let the planks lead your eye toward it. From an open section of the outer wall, include the moat and surrounding water to show the fort’s scale against the sea; stay with visitor-accessible areas.