This tiny, tropical national park has a curious history

Before it became a national park, stories of swashbuckling pirates, tales of turbulent waters, and rumors of stolen treasure haunted this seven-island archipelago some 70 miles off the coast of Florida, in the Gulf of Mexico.

During the 1600s and 1700s, the Straits of Florida were dotted with Spanish treasure ships sailing between Cuba and Florida—a prime hunting ground of pirates. Later, “wreckers” made a living salvaging and recovering cargo from sunken ships. Wrecking became so profitable (and regulated) that Key West became one of the richest cities, on a per capita basis, during the 19th century.

(Related: Here’s where to see thrilling underwater shipwrecks around the world.)

Pirates and wreckers no longer ply the waters around Dry Tortugas, but hidden treasure still calls to those willing to search for it. In 1985, treasure hunters salvaged $450 million in silver and gold from a sunken 17th-century Spanish galleon.

Lost treasure isn’t the only thing that makes this isolated aquatic realm—it takes a two-hour-plus ferry ride to get there—so alluring. Established as a national park in 1992, Dry Tortugas is the third-largest coral barrier reef in the world and the only tropical reef in the continental United States. Despite the “dry” part of its name, the park is 99 percent underwater (bring a swimsuit).

Fighting yellow fever

In 1846, five years after Spain sold Florida to America, construction began on what is still the largest masonry fort in the Western Hemisphere. Surrounded by shallow water, Fort Jefferson juts out from the sea on Garden Key, the second-largest of the park’s seven islands.

Construction slowed down when the Civil War broke out. In need of free labor to finish the compound, Fort Jefferson turned to incarcerated laborers, and in doing so became the country’s largest military prison. President Abraham Lincoln commuted Union deserters’ executions in exchange for grueling construction labor in extremely hot conditions. Garden Key soon earned the nickname “Devil’s Island.”

(Related: Explore eight unsung sites in U.S. national parks.)

As the war ravaged the States, soldiers and prisoners on the island battled the spread of yellow fever, which began plaguing the residents in 1867. Of the 400 people living in the fort, 275 were infected and 38 people died. Dr. Samuel Mudd—who had been sentenced to Fort Jefferson for providing John Wilkes Booth medical treatment after he assassinated President Lincoln—became a hero during the epidemic. The hygienic practices he put into place as the prison’s doctor saved dozens of lives, earning him a pardon for his crimes and an early release.

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Photograph by Dennis Frates, Alamy Stock Photo

After the war, construction on Fort Jefferson came to a halt amid fears that a hurricane would wash away the stronghold or that the weight of the structure would drive Garden Key underwater. No longer finding them useful to the military, President Theodore Roosevelt designated the islands, including the fortress, a federal bird reservation in 1908.

A haven for nature

Comprised of seven keys (Garden, Loggerhead, Bush, Long, East, Hospital, and Middle), the remote archipelago remains one of the least visited national parks in the National Park System, but it teems with wildlife.

Years of commercial fishing, anchor dragging, and climate change have battered the once-thriving reef system around Garden Key. But thanks to marine scientists from organizations such as the Florida Reef Resilience Program and Florida Keys National Marine Sanctuary, as well as new protective measures—such as marking off 46 square-mile of the park as a Research Natural Area—the reefs are being restored. Divers are “coral gardening” or planting laboratory-grown coral in hopes to jump-start healthy colony growth.

(Related: Learn more about travelers helping with coral replanting around the globe.)

Coral is not the only thing making a comeback. Originally named Las Tortugas (the Turtles) for the green, hawksbill, leatherback, and loggerhead turtles that Spanish explorer Juan Ponce de León encountered here in 1513, Dry Tortugas National Park remains the most active nesting sanctuary in Florida.

As a result of active protection of marine life in the park, the four endangered species of turtle—some of which can grow to 300 pounds—have seen a substantial population increase. On Bush Key, the park protects a rookery of up to 80,000 nesting sooty terns; this is the only significant nesting ground for the tropical species in the continental U.S.

One of the best things to do outside of tern-nesting season (mid-February to mid-September) is to take a walk at low tide—when the sandbar bridge between Bush and Garden Key is not submerged—and spot some of the nearly 300 species of bird which pass through each year.

Plan your trip

Dry Tortugas National Park is open year-round, but late spring (peak window to witness bird migrations) and early summer (when to see the greatest concentration of the park’s namesake) are the best times to explore the area.

Due to the park’s remote location and limited transportation options, make sure to plan your visit carefully. Keep in mind that this is a remote island park—no cell phone towers or public restrooms—so be prepared with snacks and water for the day. The ferry schedule (listing an approximate arrival time of 10:15 a.m. and departure time of 3 p.m.) allows for about a four-and-a-half-hour visit to the Garden Key. Camping overnight is allowed on the key, but a tent is required and individual sites are on a first-come, first-served basis. Make camper reservations when purchasing ferry tickets (limited to ten campers per ferry per day) to ensure there will be room for you and your gear.