Fort Jefferson: a walk around the fort

Welcome to Fort Jefferson, on Garden Key, about seventy miles west of Key West. This national park covers about a hundred square miles, and almost all of it is open water, with seven small islands.

In 1513, Ponce de León named these islands Las Tortugas, the turtles, for the sea turtles that nest here. Later, sailors' charts added one more word, dry, to warn them that there was no fresh water on the islands. Keep that in mind, because water comes back into this story.

Today's walk starts on the bridge over the moat, goes through the fort's entrance and follows the walkway around the edge of the parade ground inside: about four tenths of a mile, all flat, with six short stories. I'll tell you a story at each spot and stay quiet in between. The fort is open from sunrise to sunset, there's no food or drink for sale in the park, and the sun is strong, so keep your water bottle with you.

You're standing on the bridge over the moat, looking up at one of the largest forts the United States ever built.

The moat had two jobs: to protect these walls from heavy seas, and from enemy landings. The low wall across the water, the moat wall, went up between 1849 and 1851, but digging the moat to its full depth wasn't finished until 1873, and much of that digging was done by prisoners.

Now look at the brick face of the fort and its rows of openings for cannon. Each opening held hinged iron shutters, built to swing open from the blast of the gun and fall shut again. In the salty air, that iron rusted, swelled and pushed the bricks apart. The park's own sign puts it simply: behind every bulge you see in the walls, there's iron. Whole sections of wall have fallen into the moat, and the park has spent decades pulling out the old iron and rebuilding the brick, so you can pick out patches of newer, repaired wall.

The next story waits on the other side of the sally port, the fort's entrance gate, just ahead.

The harbor had a light before it had a fort. A brick lighthouse about sixty-five feet tall was finished on this island in 1826, and it stood here before the fort was built around it. The low ruins nearby are mapped as its foundations.

That first light was too short and too dim, and ships kept running onto the reefs. So in 1858 a taller, brighter lighthouse went up on Loggerhead Key, a few miles west, on the key the park calls the most dangerous of them all.

After hurricanes battered the old brick tower in the 1870s, the Lighthouse Service built a stronger one in iron, up on top of the fort's wall. That's the tower you can see on the corner bastion above the walkway. It went up in 1876, made of iron plate a quarter of an inch thick, and its lantern stands about eighty-two feet above the ground. It guided boats into this harbor until it was switched off in 1921, and after repairs more than once since, it still stands watch over the harbor.

These are the remains of the soldiers' barracks. The plan called for a building three stories high and more than three hundred feet long, big enough for ten companies of soldiers. Work began in 1847, and like almost everything here, it dragged on for decades, slowed by storms, epidemics, a shortage of money and a shortage of workers. During the Civil War, part of the unfinished building served as the fort's hospital. It wasn't counted as complete until about 1874, and in 1912 it burned down.

The war is when the fort mattered most. Union warships used this harbor to blockade Southern shipping, and the fort became a prison, mainly for Union deserters.

All around the parade ground are the long rows of brick arches. Those are the gunrooms, called casemates, each one built for a cannon facing the sea. The park's sign by the moat explains why the upper gunrooms were never finished: as the walls got heavier, the sand underneath shifted and the foundations settled, and in 1865 the engineers, afraid to add more weight, left the second tier unfinished.

This big brick building is the large magazine, meant to be the fort's main powder store, about fifty-two by seventy-one feet. It was built with heavy, barrel-vaulted brick arches covered in concrete, designed to be shell-proof, and prison labor helped turn its great inner arch, about thirteen and a half feet high. Work went on until 1870, but neither of the parade-ground magazines was ever truly finished, and by 1891 every magazine in the fort had been emptied of powder and ammunition.

Close by stands the shot furnace. Cannonballs were heated in its oven until they glowed red, and gunners carried them with tongs to the cannon. A red-hot ball could set a wooden ship on fire, and it could skip across the water several times and still be hot enough to start a blaze. Work on the furnace here, at the north corner of the parade ground, began in April 1862. It's a reminder that this fort was built for an age of wooden ships, an age that was ending even as the bricks went up.

These ruins were the Officers' Quarters. The full plan was for a building nearly three hundred feet long, three stories of brick on concrete foundations, with a porch running the full height of the back, half-round windows over the front doors, and cut stone sills and lintels. The first section was finished in 1850. Enslaved workers and prisoners helped build it over the years, and it wasn't considered finished until 1874. Even then, only thirty-six of its sixty-eight planned rooms could be used. It burned in 1927, and what was left above ground was taken down in 1962.

This part of the parade ground also has the ruins of a smaller two-story brick building. It was built as a kitchen, but the engineers and commanding officers lived in it for years while they waited for proper quarters. One frustrated engineer wrote that his staff deserved to be treated as gentlemen, not crammed in anywhere like day laborers or prisoners. Today it rises only to the stone sills of its upstairs windows.

Remember the word dry. Out here, fresh water was the hardest thing of all. The plan was to catch rain from the fort's roof and store it in cisterns under the gunrooms, more than a hundred of them. But on the eve of the Civil War, the engineer in charge found that not one of the finished cisterns was perfectly watertight, and the water in them had turned brackish, not fit to drink or even to cook with. During the war, the garrison came to depend on steam condensers, machines that turned seawater into drinking water.

The squat brick building here is the fort's second, smaller powder magazine, built with the same vaulted, shell-proof design as the big one.

Yellow fever kept coming back. In 1873 it killed fourteen people here. The last was a twenty-two-year-old private named George Tupper, and because a hurricane was bearing down, he was buried inside the fort, near the parade ground. In 2024, park archeologists found what they believe was his empty first grave.

That's the end of our walk. The sally port and the visitor center are a short way further along this walkway. Thank you for walking around Fort Jefferson with me, and enjoy the rest of your day out here on the water.