Located some 68 miles (109 km) west of the Florida Keys, in the Gulf of Mexico, Fort Jefferson, at Dry Tortugas National Park in Florida, was built by the U.S. Navy in the mid-19th century to prevent piracy in the Caribbean.

The 7-island chain was named by Juan Ponce de León when he stumbled upon the archipelago in 1513, back when the islands were nothing more than clusters of coral inhabited by sea turtles. Due to the large population found there, he subsequently referred to the islands as "Las Tortugas" (the turtles). The island chain is designated “Dry” due to the scarcity of fresh water available there.

The park is accessible only by seaplane or boat, yet averaged some 63,000 visitors annually in the period from 2008 - 2017. Dry Tortugas is primarily a “day-trip” destination, noted for abundant sea life, tropical bird breeding grounds, colorful coral reefs, and legends of shipwrecks and sunken treasures. Popular activities include snorkeling, picnicking, birdwatching, kayaking, scuba diving, saltwater fishing and camping; overnight camping is limited to 8 primitive campsites at the Garden Key campground.

The centerpiece of the park is Fort Jefferson, a massive, unfinished coastal fortress. Located on Garden Key Island, Fort Jefferson is the third largest U.S. coastal fort, exceeded in size only by Fort Monroe, Virginia, and Fort Adams, Rhode Island.

Dry Tortugas National Park is part of the Everglades & Dry Tortugas Biosphere Reserve, established by UNESCO in 1976.

More Info: en.m.wikipedia.org