The largest all-masonry fortification in the Western world, Fort Jefferson was part of a coastal defense buildup after the War of 1812: It played an important part in protecting trade to gulf ports and in denying access and anchorage to any enemy fleet that might attempt a military blockade. Its walls are fifty feet high and eight feet thick around its half-mile perimeter, and over forty million bricks were used in its construction. It also served as a sort of "Devil’s Island" for prisoners. Its most notorious inmate was Dr. Mudd, who was imprisoned after treating Abraham Lincoln’s assassin, John Wilkes Booth, for a broken leg.

Shipwrecks started to dot the Dry Tortugas around 1622—perhaps even earlier. More than two hundred wrecks have been documented. In addition, many ships involved in privateering, smuggling, and slavery must have gone down as well, but records of such illegal activities were naturally not logged. Salvagers earned a handsome living gathering what they could from all these wrecks. With so many ships being sunk, there was little disagreement that a lighthouse was needed.

The original Garden Key lighthouse at Fort Jefferson was built of brick in 1825 and was painted white, long before the citadel existed. It stood only sixty-five feet tall and immediately spawned complaints from mariners. The keeper at the time wasn’t as diligent as most keepers; to add to the problems of an already dim light, he often neglected to clean the windows in the lantern room, leaving them covered with soot. Conditions improved when he was removed from service, but the lighthouse was still quite inadequate. In 1858, a new, taller lighthouse was built on nearby Loggerhead Key and was fitted with a first-order Fresnel lens. In the meantime, the light at Fort Jefferson was reduced to a harbor light, but it took up valuable parade ground space inside the fort. It was eventually replaced with the current lighthouse built in 1876. Made of black, boilerplate iron, it was placed on the wall of the fort. The fifty-six-foot-tall lighthouse is still lit but has not been considered an official aid to navigation since the early 1920s.

Today the fort and lighthouse remain part of one of Florida’s most interesting parks. The National Park Service manages the Fort Jefferson National Monument, which entices twenty-seven thousand visitors each year by private boat, ferry, or daily seaplane service from Key West. (The ferry takes about three hours each way.) Spring is when most tourists—many of them bird enthusiasts—visit the island. Nearly three hundred species of birds have been spotted on the Dry Tortugas. Only a stone’s throw from Fort Jefferson, is where 45,000 Brown Noddies and over 100,000 Sooty Terns nest. The islands of the Dry Tortugas are the only place in the United States where you can see these two birds and are the site of the only known nesting colony of Frigatebirds in the country.