Fort Jefferson was built between 1846 and 1875 at the edge of the main shipping route between the Gulf of Mexico and Cuba, the western Caribbean and the Atlantic Ocean. It was never completed. The weight of the brick – the largest all-masonry fort in the U.S. – and cannon were causing settling. Its wells were contaminated by salt water intrusion compounded by the fact that rainwater was filtered through local sand, salt-saturated sand.
The fort was used as a military prison during the Civil War and up to 1874. Its most famous prisoner was Dr. Samuel Mudd, who was convicted for conspiracy; he treated the fleeing John Wilkes Booth after Booth shot Abraham Lincoln.
An interesting features was that gunners behind cannons were protected the latest technology, iron shutters that would slide openwhen the cannon rolled out and closed automatically when the cannon recoiled. That too had an unforeseen effect. Over time, the rusting mechanisms expanded destroying the mortar and brick around them.
At its peak, over seventeen hundred people, soldiers and their families, resided in the fort. The never-completed fort was turned over in 1888 to be a quarantine station. In 1992, Dry Tortugas became a National Park.
After 1888, the cannons and other metals were sold for scrap. Fortunately, the huge Rodman Guns were too heavy to be carted away although they did take their carriages. After about a hundred years rusting in the sand, the Park Service began a pains-taking process to restore them (along with the fort and a few metal shutters). One archives researcher found the original Civil War plans for the gun carriage, and a new one was constructed but this time out of stainless steel to better resist the elements. Modern equipment to lift the weapon onto the wall would be too heavy to bring in and use, so they went back to the Civil War plans again and used nineteenth century war engineering to do the job.
A lighthouse was built on Garden Key in 1825, a replacement was built, and a subsequent light was placed on the fort. But it was too low to be seen far, so a 150-foot high light was built on Loggerhead Key. That one was fully automated in 1982 and still operates.
Lighthouses or not, there are several shipwrecks in the area and several small reefs which make for great snorkeling and scuba diving. The largest wreckage field is that of the Norwegian Avanti, a 261.4-foot sailing vessel believed to have gone down in 1907.Cuban refugees, safe if they could put one foot on dry U.S. soil, have landed in the park. For the rest of us, it is much easier and still well worthwhile.