Dry Tortugas National Park

Dry Tortugas National Park

Company type	National park
Industry	Conservation, Tourism
Founded	1992
Headquarters	Florida Keys , United States
Area served	Gulf of Mexico, Florida Keys
Products	Protected natural area, recreational activities (snorkeling, camping, birdwatching, scuba diving, fishing, kayaking)
Website	www.nps.gov/drto/index.htm

Dry Tortugas National Park is a U.S. national park situated roughly 70 miles west of Key West within the Gulf of Mexico. This park safeguards the Dry Tortugas islands—the westernmost and most remote cluster of the Florida Keys—along with Fort Jefferson. The coral reef systems here rank among the most pristine throughout the Florida Keys region.

Renowned for its rich marine biodiversity, essential tropical bird nesting sites, colorful coral formations, and historic shipwrecks, the park centers around Fort Jefferson. This colossal, unfinished coastal fortress stands as the largest brick masonry edifice in the Western Hemisphere, constructed from over 16 million bricks. Dry Tortugas National Park uniquely merges a largely untouched tropical environment with important historical landmarks.

Accessible exclusively via seaplane or boat, the park recorded an average annual visitation of approximately 63,000 people between 2008 and 2017. Popular pursuits include snorkeling, picnicking, birdwatching, camping, scuba diving, saltwater fishing, and kayaking. Camping overnight is confined to eight basic campsites located at Garden Key near Fort Jefferson.

The park forms part of the Everglades & Dry Tortugas Biosphere Reserve, which UNESCO designated in 1976 under its Man and the Biosphere Programme.

Geography

The Dry Tortugas comprise a small archipelago of coral islands positioned about 70 miles west of Key West, Florida, representing the westernmost boundary of the Florida Keys. Water constitutes more than 99% of the park’s total area. In 2007, the northern and western portions—including the central islands—were declared a research natural area where harvesting marine life and anchoring are prohibited; vessels must utilize designated mooring buoys or docks. Around 54% of the park remains open to fishing activities. Adjacent areas include the Florida Keys National Marine Sanctuary on the east, south, and west sides, and the Tortugas Ecological Reserve to the northwest.

The keys themselves are low-lying and irregularly shaped; some support vegetation such as mangroves, while smaller islets often lack any plant cover. Although there are officially seven islands now, historically up to eleven have appeared due to fluctuating water levels revealing or submerging land masses and sandy connections. Several smaller keys have vanished and re-emerged following hurricane events. The principal islands from west to east are Loggerhead Key, Garden Key, Bush Key, Long Key, Hospital Key, Middle Key, and East Key. The total land area fluctuates with water levels but averages approximately 144 acres.

Island	Acres	% of total
Total	144.39	100
Loggerhead Key	64.25	44.49
Garden Key	42	29.09
Bush Key	29.65	20.54
Long Key	2	1.39
Hospital Key	0.99	0.69
Middle Key	1.5	1.04
East Key	4	2.77

• Loggerhead Key, covering , is the largest island with an elevation reaching . It features the tall Dry Tortugas lighthouse.
• Garden Key, situated about 1 mile east of Loggerhead Key and home to Fort Jefferson, Florida along with an inactive lighthouse (), spans roughly , reduced from its original size due to fort construction.
• Bush Key, formerly known as Hog Island because it was used for raising hogs to supply Fort Jefferson’s prisoners, lies just east of Garden Key and occasionally connects to it via a sandbar. Its area is about , with an elevation under , and it supports a significant tern rookery closed to visitors from February through September.
• Long Key, located approximately 0.25 miles south of Bush Key’s eastern tip, has a land area near , sometimes linked to Bush Key by a sandbar.
• Hospital Key, named after a hospital built in the 1870s for Fort Jefferson patients, lies northeast of Garden and Bush Keys by about 0.5 miles. It covers nearly , with a maximum height around .
• Middle Key, positioned roughly 0.5 miles east of Hospital Key, encompasses about , though it may be submerged seasonally due to storms or tidal changes.
• East Key, about 0.25 miles east of Middle Key, measures close to , with an elevation exceeding .

The three largest western islands—Loggerhead, Garden, and Bush Keys—account for nearly 93% of the total landmass within this group.

Former islands

Several keys that once existed from west to east include:

• Southwest Key, which disappeared by 1875 and now exists as a shoal located south of Loggerhead Reef.
• Bird Key (previously known as Booby Key), situated approximately southwest of Garden Key, vanished in 1935. The names Bird Key Bank and Bird Key Harbor persist in the area. This site served as a burial ground for Union soldiers during the Civil War.
• North Key, probably the former Booby Island, currently referred to as North Key Harbor, an anchorage located WSW of Pulaski Shoal, was gone by 1875.
• Northeast Key (once called Sand Key), positioned between East and North Keys, also disappeared by 1875.

Shoals with lights

• Pulaski Shoal (also known as Pulaski Reef), marking the northeastern boundary at , is not an island but the former location of the Pulaski Shoal Light.
• Iowa Rock, situated halfway between Garden and Hospital Keys, once supported a navigational light and weather station in shallow waters; it was demolished by Hurricane Hugo, leaving behind three stumps.

Geology

The Dry Tortugas represent the westernmost part of an arcuate chain composed of Pleistocene reef and oolitic limestone islands, which are components of the approximately thick southern Florida carbonate platform, accumulating sediments since the Early Cretaceous period. Two main stratigraphic layers are exposed here: the Key Largo Limestone—reefs reaching up to 200 ft (61 m) thick made up of hermatypic corals and calcarenites—and the Miami Limestone, which is under 49 ft (15 m) thick, typically found behind the Key Largo Limestone but overlaying it in the western keys. The Miami Limestone consists of bryozoan and oolitic facies indicative of subtidal shoals. Additionally, Holocene carbonate-sand deposits primarily formed from fragmented Halimeda plates are present in Dry Tortugas. Between Dry Tortugas and Key West lies a 39 ft (12 m) thick sediment layer known as "the quicksands."

Climate

The Dry Tortugas experience a tropical savanna climate (Köppen Aw), characterized by a wet season coinciding with the Atlantic hurricane season from May through October, and a dry season spanning November to April. Although tropical storms occasionally occur, this region is Florida’s driest, receiving roughly 38 inches of precipitation annually. Sparse vegetation covers the islands due to sandy soils with rapid drainage and intense sunlight that create drought-like conditions. Temperature variations throughout the year are minimal, with average summer highs near 91°F and winter lows around 65°F. Frost has never been documented here, placing the area within hardiness zone 12a, where average yearly minimum temperatures hover around 52°F.

History

The Dry Tortugas were first sighted by Europeans when Juan Ponce de León arrived on June 21, 1513. During his visit, Ponce de León captured about 160 sea turtles, leading him to name the islands "Tortugas" (meaning turtles). The prefix Dry refers to the lack of surface freshwater sources. This name ranks as the second oldest surviving European place-name in what is now the United States.

The archipelago is notable for many significant shipwrecks dating back to the 17th century. In 1742, a vessel ran aground in the Dry Tortugas; its crew survived on Garden Key for 56 days before making their way to Jamaica.

Following the United States' acquisition of Florida from Spain in 1819, the Dry Tortugas gained strategic importance for overseeing navigation through the Straits of Florida and Gulf of Mexico. Construction began on a lighthouse at Garden Key in 1825, later supplanted by a more powerful lighthouse on Loggerhead Key in 1856.

Prominent historical visitors include John James Audubon in 1832 and Louis Agassiz in 1858.

The maritime legacy here is extensive. In 1989, Seahawk Deep Ocean Technology investigated a shipwreck believed to be part of the 1622 Spanish treasure fleet, recovering artifacts such as olive jars, copper items, gold, and silver. On September 6, 1622, the Nuestra Señora de Atocha was lost near Dry Tortugas during a hurricane. Discovered by Mel Fisher's company in 1985, the so-called "Atocha Motherlode" contained approximately 40 tons of gold and silver, over 114,000 Spanish silver coins, Colombian emeralds, and numerous other artifacts. Fisher's Salvors Inc. also uncovered wrecks related to this fleet including the Santa Margarita and the slave ship Henrietta Marie, which sank in 1700.

Fort Jefferson

Fort Jefferson stands as an enormous, incomplete coastal stronghold and is recognized as the largest brick structure in the Western Hemisphere, constructed with more than 16 million bricks.

Its construction commenced in 1847 after the United States took control, reaching approximately fifty percent completion by 1860. The workforce mainly consisted of enslaved African Americans leased from Key West and Florida owners, supplemented by Irish immigrant laborers. Enslaved labor ceased in 1863. Throughout the Civil War, the fort remained under Union authority and later functioned as a prison until 1874. Among its notable inmates was Dr. Samuel Mudd, who was implicated in the conspiracy to assassinate President Lincoln and remained incarcerated there until his pardon in 1869.

In the 1880s, the U.S. Navy established a base at Dry Tortugas featuring coaling and wireless communication stations. During World War I, a seaplane base was added but was soon decommissioned.

Between 1903 and 1939, the Carnegie Institution operated a Marine Biology Laboratory on Loggerhead Key, which became a premier center for tropical marine science with over 150 researchers involved. In 1911, the laboratory commissioned the vessel Anton Dohrn to facilitate research activities and transportation between the station and Key West. After serving in naval operations during World War I, Anton Dohrn resumed its support for scientific work until the laboratory's closure in 1939, after which it was donated to the Woods Hole Oceanographic Institution.

President Franklin D. Roosevelt visited Fort Jefferson accompanied by future Supreme Court Justice Robert H. Jackson, who later recounted this experience in his book That Man: An Insider's Portrait of Franklin D. Roosevelt.

History of African Americans on the island

Fort Jefferson's history includes African Americans who were enslaved individuals, Union soldiers, freedmen, and detainees. Beginning in 1847, the United States Army Corps of Engineers employed enslaved workers, with roughly 17% of Key West’s enslaved population leased to the Corps from 1847 through 1860. The majority were men assigned to strenuous manual labor; others served as domestic workers, boatmen, or cooks. Enslaved women typically managed washing and cooking duties. Following the Emancipation Proclamation, freed African American men enlisted in the Union Army. Near the conclusion of the Civil War, the 82nd Colored Infantry was stationed at Fort Jefferson. Additionally, between 1861 and 1871, African Americans were detained there as military prisoners.

Park history

Covering , Fort Jefferson National Monument was established by President Franklin D. Roosevelt under the Antiquities Act on January 4, 1935. It underwent expansion in 1983 and was reclassified as Dry Tortugas National Park by congressional action on October 26, 1992. The park is administered jointly with Everglades National Park, sharing a superintendent. Its mission includes protecting island and marine habitats, preserving Fort Jefferson along with submerged cultural assets such as shipwrecks, while permitting controlled public visitation.

During the federal government shutdowns of 1995–1996, Dry Tortugas closed alongside other national parks. Concerned about tourism losses, residents of Key West attempted to fund keeping it open but found no official recipient for their donations. Acting under the satirical banner of the Conch Republic, they organized a flotilla to Fort Jefferson to reopen access; officials who tried to enter were cited but charges were ultimately dismissed.

The park also functions as a landing site for Cuban migrants arriving in homemade boats known as "chugs," presenting operational challenges due to limited resources and its distance from Coast Guard or Border Patrol support. Communications with Key West rely on satellite voice-over-IP technology combined with radio relays via an abandoned Air Force tower.

Visitor numbers peaked at 83,704 in 2000 but subsequently declined to an average of around 63,000 annually between 2007 and 2016.

In August 2004, Hurricane Charley made direct landfall on Dry Tortugas; shortly afterward, a Cessna aircraft crashed nearby during filming of CrossBones, resulting in the death of cinematographer Neal Fredericks. More recently, Hurricane Ian directly affected the islands in September 2022.

Ecology

The Dry Tortugas island group represents a transitional ecosystem between subtropical and tropical zones, supporting species that seldom breed elsewhere within the continental United States or its adjacent marine environments.

In January 1977, a severe cold wave caused catastrophic damage, destroying approximately 96% of the shallow-water branching coral and converting vast coral reefs into scattered rubble. Currently, Dry Tortugas National Park predominantly features isolated patch reefs alongside areas of broken branching coral debris.

Birds

Within Dry Tortugas National Park, 299 bird species have been documented, with eight species regularly nesting: the sooty tern, brown noddy, brown pelican, magnificent frigatebird, masked booby, roseate tern, bridled tern, and mourning dove. The park uniquely supports the only nesting populations of sooty tern, brown noddy, magnificent frigatebird, and masked booby within the contiguous United States.

Birdwatching activity reaches its highest levels each spring in April when numerous migratory birds pass through. Many avian visitors settle on the parade grounds of Fort Jefferson, offering exceptional opportunities for close observation. Frequently observed warblers include the northern parula, American redstart, prairie warbler, hooded warbler, palm warbler, among others, with over twenty additional warbler species also recorded. Raptors preying on these songbirds are commonly seen as well. Seasonal birding excursions often report daily species tallies surpassing 100.

Invasive species and eradication efforts

A proactive removal initiative has successfully eliminated invasive Casuarina trees and agave plants from Loggerhead Key through mechanical cutting combined with herbicide application. The presence of Pterois (lionfish) in park waters has led the National Park Service to develop (as of 2015) a management strategy aimed at controlling this invasive fish species within Dry Tortugas and Everglades National Park.

Visiting

The majority of visitors arrive at Dry Tortugas National Park via boat or seaplane departing from Key West. Authorized transport options include the Yankee Freedom III catamaran, private boat charters, and seaplane flights. There is no road access to the islands, and motor vehicles are prohibited.

Amenities inside the park are minimal; guests must bring their own provisions such as food and water. Lodging and dining facilities are available only in Key West. Primitive camping is permitted on Garden Key.

See also

• Florida Keys National Marine Sanctuary
• List of national parks of the United States

External links

• Official website