Dry Tortugas National Park is a United States national park located about 68 miles (109 km) west of Key West in the Gulf of Mexico. The park protects Fort Jefferson and the Dry Tortugas islands, which are the westernmost and most remote of the Florida Keys. The group of islands has coral reefs that are among the least disturbed in the Florida Keys.

The park is known for its rich sea life, areas where tropical birds breed, colorful coral reefs, and shipwrecks with sunken treasures. The main attraction is Fort Jefferson, a large but incomplete coastal fortress. Fort Jefferson is the largest brick structure in the Western Hemisphere, made of more than 16 million bricks. Dry Tortugas National Park is special because it combines a tropical ecosystem that has remained largely undisturbed with important historical items. The park can only be reached by seaplane or boat and had about 63,000 visitors each year from 2008 to 2017. Activities include snorkeling, picnicking, birdwatching, camping, scuba diving, saltwater fishing, and kayaking. Overnight camping is limited to eight basic campsites at the Garden Key campground, which is just south of Fort Jefferson.

Dry Tortugas National Park is part of the Everglades & Dry Tortugas Biosphere Reserve, created by UNESCO in 1976 as part of its Man and the Biosphere Programme.

Geography

The Dry Tortugas is a group of small coral islands located about 70 miles (110 km) west of Key West, Florida. These islands are the westernmost part of the Florida Keys, though some reefs and underwater areas extend farther west beyond the park.

The park covers more than 99% water. In 2007, the northern and western parts of the park, including the central islands, were set aside as a 46-square-mile (120 km²) research natural area. In this area, no marine life may be taken, and boats cannot anchor. Boats must use special mooring buoys or docks to tie up. About 54% of the park is open for fishing. The park is bordered on the east, south, and west by the Florida Keys National Marine Sanctuary and on the northwest by the Tortugas Ecological Reserve.

The islands are low and uneven. Some have small mangrove trees and other plants, while the smallest islands have only grass or no vegetation. There are seven named islands, but the number has changed over the past two centuries. The islands shift in size and shape as water levels rise and fall, sometimes revealing or hiding smaller islands and creating or removing sand bridges between them. Some islands have disappeared and reappeared due to hurricanes. From west to east, the major islands are Loggerhead Key, Garden Key, Bush Key, Long Key, Hospital Key, Middle Key, and East Key. The total land area in the park changes with water levels and is about 144 acres (58 hectares).

• Loggerhead Key is the largest island, covering 26 hectares (64 acres). It is 250 by 1,200 meters (820 by 3,940 feet) in size and has the highest point in the Dry Tortugas at 10 feet (3 meters). The Dry Tortugas Lighthouse, 46 meters (151 feet) tall, is located here.
• Garden Key is the second-largest island, covering 17 hectares (42 acres). It is 400 by 500 meters (1,300 by 1,600 feet) in size and is home to Fort Jefferson and an inactive lighthouse. The island was originally larger before Fort Jefferson was built.
• Bush Key is the third-largest island, covering 12 hectares (30 acres). It is 150 by 900 meters (490 by 2,950 feet) in size and less than 1 meter (3 feet 3 inches) high. This island is a nesting site for terns and is closed to visitors from February to September to protect these birds.
• Long Key is 50 by 200 meters (160 by 660 feet) in size and covers 8,000 square meters (2 acres). It is sometimes connected to Bush Key by a sandbar.
• Hospital Key was named for a hospital built for Fort Jefferson prisoners in the 1870s. It is 4,000 square meters (0.99 acres) in size and 1 meter (3 feet 3 inches) above sea level at its highest point.
• Middle Key is 6,000 square meters (1.5 acres) in size and 90 meters (300 feet) long. It is not always above sea level due to seasonal changes, storms, and tides.
• East Key is 100 by 200 meters (330 by 660 feet) in size and covers 1.6 hectares (4 acres). It is over 2 meters (6 feet 7 inches) high.

The three largest islands—Loggerhead Key, Garden Key, and Bush Key—make up about 93% of the total land area in the Dry Tortugas.

Some islands that once existed are no longer present:
– Southwest Key disappeared by 1875 and is now a shallow area south of Loggerhead Reef.
– Bird Key (formerly Booby Key) was located 1.5 km (0.93 mi) southwest of Garden Key but disappeared in 1935. The area is now called Bird Key Bank and Bird Key Harbor. This island was the site of Union soldiers’ graves during the Civil War.
– North Key was likely the same as former Booby Island and is now called North Key Harbor. It disappeared by 1875.
– Northeast Key (earlier called Sand Key) was between East Key and North Key but disappeared by 1875.

Pulaski Shoal (Pulaski Reef) marks the northeast edge of the group at 24°41′36″N 82°46′24″W. It is not an island but was once the location of a lighthouse. Iowa Rock, halfway between Garden Key and Hospital Key, was a site for a navigational light and weather station. It was destroyed by Hurricane Hugo, leaving only three stumps.

Geology

The Dry Tortugas are the western part of a curved chain of islands made of Pleistocene reef and oolitic limestone. The eastern end of this chain is near Miami. These Florida Keys are the visible part of a thick southern Florida carbonate platform that is 3.7 miles (6.0 kilometers) thick. This platform has been building up layers of sediment since the Early Cretaceous period. Two layers of rock are visible on the surface: the Key Largo Limestone and the Miami Limestone. The Key Largo Limestone forms reefs up to 200 feet (61 meters) thick, running parallel to the edge of the continental shelf. It is made of hermatypic corals and a type of limestone called calcarenites. The Miami Limestone is less than 49 feet (15 meters) thick. It is usually found behind the Key Largo Limestone reef but lies on top of it in the western part of the keys. It is made of two types of rock layers: one with bryozoans and another with oolites, and it forms a shallow underwater area called a subtidal shoal. In the Dry Tortugas, there are excellent examples of Holocene carbonate-sand deposits. These deposits are mainly made of broken pieces of Halimeda plates. Between the Dry Tortugas and Key West, there is a 39-foot (12-meter) thick layer of these sand deposits, known as "the quicksands."

Climate

Dry Tortugas has a tropical savanna climate (Aw), with a rainy season that happens at the same time as the Atlantic hurricane season, from May to October. The dry season lasts from November through April. Even though the area sometimes experiences tropical weather systems, Dry Tortugas is the driest place in Florida, receiving about 38 inches (970 mm) of rain each year. There are no large forests or jungles on the islands, and the sandy soil, which drains water quickly, along with strong sunlight, make drought-like conditions common. Temperatures do not change much throughout the year. In summer, high temperatures reach about 91°F (33°C), and in winter, low temperatures stay around 65°F (18°C). Like the rest of the lower keys, there has never been a recorded frost or freeze. The hardiness zone is 12a, with an average yearly minimum temperature of 52°F (11°C).

History

The first European to see the Dry Tortugas was Juan Ponce de León, who visited on June 21, 1513. Ponce de León caught 160 sea turtles there and later called the islands "Tortugas" because of the turtles. The name "Dry" comes from the lack of fresh water on the islands. This name is the second oldest European place name still used in the United States.

The Dry Tortugas include many historically important shipwrecks from the 17th century to today. In 1742, the ship HMS Tyger wrecked in the Dry Tortugas. The crew who survived stayed on Garden Key for 56 days. They fought a battle with a Spanish sloop before leaving in several boats to Jamaica.

Florida was bought from Spain by the United States in 1819. The Dry Tortugas were considered important for controlling the Straits of Florida and the Gulf of Mexico. Work on a lighthouse on Garden Key began in 1825. In 1856, a new and stronger lighthouse was started on Loggerhead Key to replace the one on Garden Key.

John James Audubon visited the Tortugas in 1832, and Louis Agassiz visited in 1858.

The Dry Tortugas have a rich maritime history. In 1989, Seahawk Deep Ocean Technology explored a shipwreck believed to be part of the 1622 Spanish treasure fleet. The wreck, located 1,332 feet (406 meters) underwater, had items like olive jars, copper, gold, silver, glass, and other artifacts. On September 6, 1622, the ship Nuestra Señora de Atocha was wrecked by a hurricane near the Dry Tortugas, about 35 miles (56 kilometers) west of Key West. Mel Fisher and his team discovered the wreck on July 20, 1985. The treasure, called "The Atocha Motherlode," included about 40 tons of gold and silver, 114,000 Spanish silver coins, gold coins, Colombian emeralds, and other items. Fisher’s team also found remains of other shipwrecks, including the Santa Margarita and the Henrietta Marie.

Fort Jefferson is a large but unfinished coastal fortress. It is the largest masonry structure in the Western Hemisphere and is made of more than 16 million bricks.

Plans for a fort began soon after the United States took control of Florida. Construction started in 1847, and by 1860, half of the work was done. Most of the workers were enslaved Black people hired from their owners in Key West and other parts of Florida. Some White workers, mostly Irish immigrants, were also employed. Enslaved labor was stopped in 1863. The fort stayed in Union control during the Civil War and later served as a prison until it was abandoned in 1874. Dr. Samuel Mudd, who treated John Wilkes Booth after Lincoln’s assassination, was imprisoned here for conspiring with others. He was pardoned in 1869 after helping stop a disease outbreak. Another prisoner was George St. Leger Grenfell, a leader of the "Chicago Conspiracy," who is said to have drowned while trying to escape.

During the 1880s, the Navy built a base in the Dry Tortugas and later set up a coaling (refueling) station and a wireless (radio) station there. During World War I, a seaplane base was built but was later abandoned.

From 1903 to 1939, the Carnegie Institution of Washington operated the Marine Biology Laboratory on Loggerhead Key. The lab became one of the best-equipped marine research stations in the tropical world. Over 150 researchers used the lab for studies. In 1911, the lab built a ship named Anton Dohrn in Miami for research and travel. The ship helped the lab until it closed in 1939 and was donated to the Woods Hole Oceanographic Institution.

A visit to Fort Jefferson by President Franklin D. Roosevelt and future Justice Robert H. Jackson is described in Jackson’s book That Man: An Insider's Portrait of Franklin D. Roosevelt.

Fort Jefferson was home to African Americans not only as enslaved people but also as Union soldiers, freedmen, and prisoners. Starting in 1847, the U.S. Army Corps of Engineers hired enslaved laborers. Between 1847 and 1860, about 17% of Key West’s enslaved people were leased to work on the fort. Most enslaved workers were men who did hard, unskilled labor. Some worked as domestic servants, boatmen, or cooks. Enslaved women also worked, doing laundry and some cooking. After the Emancipation Proclamation, some African American men joined the Union Army. The 82nd Colored Infantry was stationed at Fort Jefferson near the end of the Civil War. Between 1861 and 1871, African Americans were held as military prisoners at the fort.

Park history

Fort Jefferson National Monument covers 47,125 acres (73.6 square miles; 190.7 square kilometers). President Franklin D. Roosevelt established it under the Antiquities Act on January 4, 1935. In 1983, the monument was expanded and renamed Dry Tortugas National Park on October 26, 1992, by a law passed by Congress. Dry Tortugas is managed together with Everglades National Park, and they share a single park manager. The park was created to protect the islands and ocean life of the Dry Tortugas, to preserve Fort Jefferson and underwater historical items like shipwrecks, and to allow visitors in a controlled way.

During the U.S. government shutdowns in 1995 and 1996, Dry Tortugas was closed, along with all other national parks. Residents of Key West, Florida, worried about the impact on their economy, which depends on tourism, and raised money to keep the park open. This effort was inspired by the Smithsonian Institution, which collected private donations to keep its museums open during the shutdown.

When no one accepted the money to reopen the park, Key West residents, acting under the group called the Conch Republic, sent a group of civilian and fire department boats to Fort Jefferson to reopen the park. Officials tried to enter the fort but were cited for breaking rules. The citation was challenged in court the next year, and the case, The United States of America v. Peter Anderson, was dropped quickly.

The park is a place where immigrants from Cuba arrive in homemade boats called "chugs." Helping these migrants is a challenge for Dry Tortugas, as the park has few resources and is far from Coast Guard or Border Patrol units. Communication with Key West uses a satellite phone system and a radio relay system that uses an old Air Force tower between Key West and the Dry Tortugas. These systems can cause delays and unclear messages.

Visits to the park increased for many years, reaching 83,704 in 2000. After that, the number of visitors slowly decreased, averaging about 63,000 per year from 2007 to 2016.

In August 2004, Hurricane Charley hit the Dry Tortugas directly. The next day, a Cessna airplane crashed into the water near the islands, killing cinematographer Neal Fredericks while he was filming for the movie CrossBones. In September 2022, Hurricane Ian struck the islands directly again.

Ecology

The Dry Tortugas archipelago is a mix of subtropical and tropical environments, home to species that rarely breed or are found in other parts of the continental United States or nearby islands and waters.

In January 1977, a cold wave destroyed 96 percent of the shallow-water branching coral, turning once-large coral formations into rubble. Today, Dry Tortugas National Park includes patch reefs and coral rubble.

The park has an official list of 299 bird species. Only eight of these nest regularly within the park: sooty tern, brown noddy, brown pelican, magnificent frigatebird, masked booby, roseate tern, bridled tern, and mourning dove. The park is the only place in the contiguous United States where sooty tern, brown noddy, magnificent frigatebird, and masked booby nest.

Birdwatching activity is highest in spring, especially in April, when many migratory birds pass through the park in one day. Many birds land near Fort Jefferson’s parade grounds, where they can be seen up close. Common migratory warblers include northern parula, American redstart, prairie warbler, hooded warbler, palm warbler, black-and-white warbler, common yellowthroat, yellow-rumped warbler, ovenbird, northern waterthrush, black-throated blue warbler, blackpoll warbler, and Cape May warbler. Over 20 other warbler species have also been spotted. Several raptor species are often seen hunting songbirds. Each year, bird guides lead tours in April and early May, when daily bird lists often include 100 or more species.

An active removal program has eliminated invasive Casuarina trees and agave from Loggerhead Key using cutting and herbicides. Lionfish, also known as Pterois, have been found in the park’s waters. In 2015, the National Park Service was reviewing a plan to manage the spread of lionfish in Dry Tortugas National Park and Everglades National Park.

Visiting

Most visitors reach Dry Tortugas National Park by boat or seaplane from Key West. Official ways to travel to the park include the Yankee Freedom III catamaran, renting private boats, and using seaplane services. Other options are approved private boat charters. There are no roads to Dry Tortugas, and cars cannot reach the islands.

Inside the park, services and supplies are limited. Visitors must bring their own food, water, and other items needed during their stay. The nearest restaurants and hotels are in Key West. However, basic camping areas are available on Garden Key within the park.