The lighthouse on Loggerhead Key was built in 1858 to replace the Fort Jefferson light because even with this light, ships still ran aground on the surrounding nearly eighty-square-mile grouping of reefs, shoals, and islands known as the Dry Tortugas. (Then the lighthouse at the fort was reduced to a harbor light.)
A red sector was placed in the lens in 1893 to alert mariners of a reef just offshore from the lighthouse. The Loggerhead Key light was electrified in 1931, and its three-million-candlepower light made it the most powerful light in the United States at that time. A modern optic lens replaced the original first-order Fresnel lens in 1986 and is now on display at the Coast Guard Aid to Navigation School in Yorktown, Virginia.
The hurricane of 1873 inflicted heavy damage on the tower at Loggerhead Key. The South Florida lighthouse webpage says, "A decade and a half after the 151-foot-tall lighthouse was built, mortar between the bricks started to erode and cracks began to appear because of exposure to wind-driven rain. To remedy the continuous cracking, nine feet of brick work was removed from the top of the lighthouse, and iron rods were inserted for reinforcement. Then, one section at a time, masonry was chiseled out in the lower sections, rods were implanted, and bricks were replaced, but the lighthouse continued to vibrate in strong winds. Despite its problems, the lighthouse continues to stand and function today, marking the entrance to the Gulf of Mexico."
Loggerhead Key was named because it was a nesting ground for turtles. They were used for meat but when Loggerhead Key was included in the National Park, the turtles can nest undisturbed.
Loggerhead Key is open for day use only. There are no public overnight accommodations on Loggerhead Key. All building and structures are closed to entry unless you are accompanied by a park employee. The pier is closed to public docking and you must enter by anchoring offshore and approaching the beach in small boats.
Although it is difficult to be very 'off the beaten track' here, many people may miss the fact that there is a very good informational video in the National Park visitor's information center. There are also books full of documentation and information on the building of the fort, people who were stationed or lived here, and the birds
Most national parks have a similar video and information.