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Dry Tortugas
Location end of the Florida Keys, United States
Archipelago Florida Keys
Adjacent bodies of water Gulf of Mexico
United States
Demonym American
  • Regular: 0
  • Seasonal: varies
Additional information
Time zone
 • Summer (DST)

The Dry Tortugas are a small group of islands, located in the Gulf of Mexico at the end of the Florida Keys, United States, about 67 miles (108 km) west of Key West, and 37 miles (60 km) west of the Marquesas Keys, the closest islands. Still further west is the Tortugas Bank, which is submerged. The first Europeans to discover the islands were the Spanish in 1513, led by explorer Juan Ponce de León. They are an unincorporated area of Monroe County, Florida, and belong to the Lower Keys Census County Division. With their surrounding waters, they constitute the Dry Tortugas National Park.


The keys are low and irregular. Some keys have thin growths of mangroves and various other vegetation, while others have only small patches of grass or are devoid of plant life. In general, they rise abruptly from relatively deep water. They are continually changing in size and shape. The Tortugas Atoll has had up to 11 islets during the past two centuries. Some of the smaller islands have disappeared and reappeared multiple times as a result of hurricane impact.


The total area of the islets, some of which are little more than sand bars just above the water mark, is about 580,000 square meters (143 acres). Their area changes over time as wind and waves reshape them. There are seven islets, which are from West to East: 1 lb (0.45 kg)

  • Loggerhead Key, 250 by 1,200 m (820 by 3,940 ft) in size, with an area of 260,000 m2 (2,800,000 sq ft) is the largest. This island has the highest elevation in the Dry Tortugas, at 10 feet (3.0 m). The Dry Tortugas lighthouse, 46 m (151 ft) 46 meters high, is on this island.
  • Garden Key, with Fort Jefferson and the inactive Garden Key lighthouse (20 m (66 ft)). It is 4 km (2.5 mi) east of Loggerhead Key. Garden Key is the second largest island in the chain, at 400 by 500 m (1,300 by 1,600 ft) in size, with an area of 170,000 m2 (1,800,000 sq ft). The original size, before construction of Fort Jefferson, has been estimated at 30,350 to 35,610 m2 (326,700 to 383,300 sq ft).
  • Bush Key, formerly named Hog Island because of the hogs that were raised there to provide fresh meat for the prisoners at Fort Jefferson, just a few meters east of Garden Key. At times, Bush Key is connected to Garden Key by a sand bar. The island is the third largest, 150 by 900 m (490 by 2,950 ft), area 120,000 m2 (1,300,000 sq ft), less than 1 m (3 ft 3 in) high. Bush Key is the site of a large tern rookery. It is closed to visitors from April to September to protect nesting sooty terns and brown noddys.
  • Long Key,59 m (194 ft) south of the eastern end of Bush Key, 50 by 200 m (160 by 660 ft) in size, area of 8,000 m2 (86,000 sq ft).
  • Hospital Key, so called because a hospital for the inmates of Fort Jefferson had been built there in the 1870s. The island was formerly called Middle Key or Sand Key. It lies 2.5 km (1.6 mi) northeast of Garden Key and Bush Key, 70 m (230 ft), area 4,000 m2 (43,000 sq ft), and is 1 m (3 ft 3 in)high at its highest point.
  • Middle Key, 2.5 km (1.6 mi) east of Hospital key, 90 m (300 ft), area 6,000 m2 (65,000 sq ft), due to various seasonal changes, storm patterns and tidal cycles it is not always above sea level, disappearing for weeks or months only to reappear again.
  • East Key, 2 km (1.2 mi) east of Middle Key, 100 by 200 m (330 by 660 ft), area 16,000 m2 (170,000 sq ft), over 2 meters high

The three westernmost keys, which are also the three largest keys (Loggerhead Key, Garden Key, and Bush Key), make up about 93 percent of the total land area of the group.

Former islands

Formerly existing keys were, from West to East:

  • Southwest Key, disappeared by 1875, today a shoal south off Loggerhead Reef
  • Bird Key (formerly Booby Key), was about 1.5 km (0.93 mi) southwest of Garden Key, disappeared in 1935, current names in the area are Bird Key Bank and Bird Key Harbor. The Key was the site of numerous Union solder's graves during the Civil War.
  • North Key, probably identical with former Booby Island, current name in the area is North Key Harbor, an anchorage WSW of Pulaski Shoal, disappeared by 1875
  • Northeast Key (earlier called Sand Key), was between East Key and North Key, slightly to the North, disappeared by 1875

Shoals with lights


Climate data for Dry Tortugas, 1981-2010 normals, extremes 1950-present
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 89
Average high °F (°C) 73.6
Average low °F (°C) 63.8
Record low °F (°C) 46
Precipitation inches (mm) 2.61
Avg. rainy days (≥ 0.01 in) 6.4 5.6 5.5 3.7 4.3 8.3 9.4 11.3 13.3 8.7 5.4 5.9 87.8
Source: [1]


Spanish explorer Ponce de León gave the Dry Tortugas their name on his first visit in 1513. The name is the second oldest surviving European place-name in the US. They were given the name Las Tortugas (The Turtles) due to 170 sea turtles taken on the islands and shoals by de León's men. Soon afterward, the word "Dry" was added to the name, to indicate to mariners the islands' lack of springs.

In 1742 HMS Tyger wrecked in the Dry Tortugas. The stranded crew lived on Garden Key for 56 days, and fought a battle with a Spanish sloop, before sailing to Jamaica in several boats.

John James Audobon visited the Tortugas in 1832 and so did Louis Agassiz in 1858.

The United States government never completed Fort Jefferson after 30 years on Garden Key. This bastion remained in Union hands throughout the Civil War. It later was used as a prison until abandoned in 1874. Dr. Samuel Mudd, famous for being the doctor who treated John Wilkes Booth in the wake of the Lincoln assassination, was imprisoned here until early 1869. During the 1880s, the Navy established a base in the Dry Tortugas, and it subsequently set up a coaling (refueling) and a wireless (radio) station there as well. During World War I, a seaplane base was established in the islands, but it was abandoned soon thereafter.

Fort-Jefferson Dry-Tortugas
Fort Jefferson on Garden Key, from northeast

From 1903 until 1939 the Carnegie Institution of Washington operated the Marine Biology Laboratory on Loggerhead Key which "...quickly became the best-equipped marine biological station in the tropical world.” Through the years, over 150 researchers used the facilities to perform a wide range of research. In June 1911 the laboratory built a vessel in Miami, Anton Dohrn, for use by researchers as well as logistics between the station and Key West. The vessel, excepting a period of World War I service with the Navy, supported the laboratory's work until closure in 1939 and donation of Anton Dohrn to the Woods Hole Oceanographic Institution.

An account of a visit to the fort at the Dry Tortugas by President Franklin D. Roosevelt and Justice-to-be Robert H. Jackson can be found in Jackson's book That Man: An Insider's Portrait of Franklin D. Roosevelt.

The Dry Tortugas are also rich in maritime history. In 1989 Seahawk Deep Ocean Technology explored a shipwreck believed to be part of the 1622 Spanish treasure fleet. The wreck located in 1332' (406m) of water, yielded olive jars, copper, gold, silver, glass and other cultural artifacts. On September 6, 1622, the Nuestra Señora de Atocha was driven by a severe hurricane onto a coral reef near the Dry Tortugas, about 35 mi (56 km) west of Key West. Mel Fisher and his company discovered the wreck July 20, 1985. The estimated $450 million cache recovered, known as "The Atocha Motherlode," included 40 tons of gold and silver; there were some 114,000 of the Spanish silver coins known as "pieces of eight", gold coins, Colombian emeralds, gold and silver artifacts, and 1000 silver ingots. In addition to the Atocha, Fisher's company, Salvors Inc., found remains of several nearby shipwrecks, including the Atocha's sister galleon the Santa Margarita, lost in the same year, and the remains of a slave ship known as the Henrietta Marie, lost in 1700.

In August 2004, the Dry Tortugas were directly struck by Hurricane Charley. The following day, a Cessna airplane crashed into the water near the islands, killing cinematographer Neal Fredericks while he was filming scenery for the feature film CrossBones.

In popular culture

  • In Robert Louis Stevenson's Treasure Island (1884), Billy Bones speaks of the Dry Tortugas in his drunken tales.
  • The islands are the location for Nevada Barr's 2003 novel, Flashback, and a key location (and, with the history of Fort Jefferson, a key plot point) in Brad Meltzer's 2015 thriller, The President's Shadow.
  • The pirate Edward Kenway, the main character of Assassin's Creed IV: Black Flag, visits the Dry Tortugas as well as other locales, throughout his adventure.
  • The Dry Tortugas are featured in Bob and Ray's "Mary Backstage" serial.
  • Garden Key was the setting for James Fenimore Cooper's Jack Tiers novel.


The Dry Tortugas are 70 miles (110 km) west of Key West, Florida. Visiting the park by private boat is difficult because of its distance, so most visitors come by ferry, catamaran, or seaplane from Key West. Other methods of visiting the Dry Tortugas include chartering of authorized and approved private vessels. Only certain companies have access to fish or dive near the Dry Tortugas. Official ferry and transportation services to the Dry Tortugas includes the Yankee Freedom III catamaran, private vessel chartering and seaplane services.


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