Dry Tortugas National Park & Fort Jefferson Guide

Named after Thomas Jefferson, construction on Fort Jefferson began in 1846 on Garden Key, a strategic crossroad between the Gulf of Mexico, the Atlantic Ocean, and the Caribbean Sea. Designed as a massive tiered hexagon with gunrooms known as casemates, the fort was engineered to control shipping channels entering the Gulf and protect American commercial trade.

Despite three decades of construction and the placement of over 16 million red bricks shipped by sea from Pensacola and Maine, the fortress was never completely finished. Advances in rifled artillery during the Civil War rendered brick masonry fortifications obsolete before its armaments were fully installed. Throughout the Civil War, Union forces held Fort Jefferson continuously, using it as a secure coaling station and military prison.

Following the assassination of President Abraham Lincoln in April 1865, four civilian conspirators were sentenced to life imprisonment at Fort Jefferson, including Dr. Samuel Mudd—the Maryland physician who set John Wilkes Booth's fractured leg.

Dr. Mudd spent four miserable years imprisoned in an unventilated ground-level cell facing the moat. However, during the devastating Yellow Fever epidemic of 1867, which killed the post surgeon and dozens of soldiers, Dr. Mudd took charge of medical operations and saved dozens of lives. In recognition of his courage and medical service, President Andrew Johnson pardoned Mudd in 1869. Today, visitors can walk right into Dr. Mudd's preserved cell on the second tier of the fort.

Dry Tortugas offers the finest coral reef snorkeling in the continental United States. Because the park lies 70 miles west of Key West, oceanic currents are pristine, free from agricultural runoff and shoreline development.

The best snorkeling lies in two distinct zones accessible right from the beach:

• The Moat Wall: Swimming along the outer moat wall exposes a vibrant vertical reef community. Encrusting corals, sea fans, and purple sea plumes grow directly on the 19th-century submerged brickwork. Snorkelers routinely encounter juvenile barracudas, schools of sergeant majors, and vibrant parrotfish in water just 4 to 8 feet deep.
• The Old Coaling Docks: To the west of the fort, the submerged pilings of the historic Navy coaling docks form an artificial reef that shelters giant goliath groupers (often weighing 200 to 400 lbs), green sea turtles, and massive schools of silver baitfish. Stay at least 15 feet clear of pilings to avoid sharp barnacles in moving currents.

Critical realities about Garden Key that guidebook summaries frequently omit:

• Ponce de León named it for turtles and thirst: In 1513, Spanish explorer Ponce de León discovered the islands and named them Las Tortugas for the 170 sea turtles his crew captured. Nautical charts later added 'Dry' as a stark warning to mariners that the coral cays held zero fresh water springs (Source: National Park Service Historical Archives).
• The fort was sinking during construction: Engineers realized too late that 16 million heavy bricks resting on unconsolidated sand and coral rubble caused the foundation to settle unevenly, cracking outer cisterns and leaking fresh rainwater into the saltwater moat (Source: U.S. Army Corps of Engineers Historical Record).
• Seaplane arrives before the ferry: If you fly via seaplane on the morning departure, you arrive on Garden Key nearly two hours before the Yankee Freedom ferry docks, giving you the entire 16-acre fortress completely to yourself (Source: Key West Seaplane Operations).
• Sea sickness on the Gulf crossing: The 70-mile open water transit crosses the Rebecca Shoal channel. When winter winds blow 15-20 knots, 4-to-6-foot ocean swells can cause motion sickness. Taking non-drowsy Dramamine before departing Key West harbor is strongly advised (Source: Yankee Freedom Crew Guidelines).
• Pack-it-in, pack-it-out rule: There are zero trash receptacles anywhere on Garden Key. Every empty soda can, plastic wrapper, and napkin you bring ashore must be carried back aboard the vessel (Source: NPS Leave No Trace Regulations).

Garden Key has no store, no gear rental, and no fresh water outside the ferry. Pack these essentials: