The park preserves Fort Jefferson and the several Dry Tortugas islands, the westernmost and most isolated of the Florida Keys.

The park is noted for abundant sea life, tropical bird breeding grounds, colorful coral reefs, and shipwrecks and sunken treasures.

They represent the westernmost extent of the Florida Keys, though several reefs and submarine banks continue westward outside the park, beyond the Tortugas.

The northern and western portions of the park, including the central island group, were designated a 46-square-mile (120 km2) research natural area in 2007, in which no marine life may be taken, nor may vessels anchor.

[9] 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.

Formerly existing keys were (from west to east): The Dry Tortugas are the western extension of an arcuate chain of Pleistocene reef and oolitic limestone islands, with the eastern limit in the vicinity of Miami.

The Key Largo Limestone are reefs up to 200 ft (61 m) thick, parallel to the shelf edge, consisting of hermatypic corals and calcarenites.

Additionally, excellent examples of Holocene carbonate-sand deposits are found in the Dry Tortugas, consisting mainly of disarticulated Halimeda plates.

Despite occasional exposure to tropical systems, the Dry Tortugas is the driest place in Florida with an annual precipitation of about 38 in (970 mm).

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.

The wreck located in 1,332 ft (406 m) of water, yielded olive jars, copper, gold, silver, glass and other cultural artifacts.

Workers consisted mostly of enslaved Black people hired from their owners in Key West and other parts of the State of Florida.

[22] Dr. Samuel Mudd, famous for being the doctor who treated John Wilkes Booth in the wake of the Lincoln assassination, was imprisoned here for conspiracy with three others until early 1869, when he was pardoned in 1869 after averting a viral outbreak.

[30] Also imprisoned was a leader of the "Chicago Conspiracy", Englishman George St. Leger Grenfell, who is supposed to have drowned having escaped in a small boat.

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.

[32] 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.

[33] 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.

[29] Comprising 47,125 acres (73.6 sq mi; 190.7 km2), Fort Jefferson National Monument was designated by President Franklin D. Roosevelt under the Antiquities Act on January 4, 1935.

[38] The park was established to protect the island and marine ecosystems of the Dry Tortugas, to preserve Fort Jefferson and submerged cultural resources such as shipwrecks, and to allow for public access in a regulated manner.

Seeing this as having a damaging effect on their tourism-dependent economy, the residents of Key West, Florida, raised money to keep Dry Tortugas open.

The citation was contested in court the following year, and the resultant case, The United States of America v. Peter Anderson, was quickly dropped.

Receiving and housing the migrants is a particular problem for Dry Tortugas, which has limited resources for such arrivals and which is several hours from the nearest Coast Guard or Border Patrol units.

[41] The Dry Tortugas archipelago is classified as a borderline subtropical—tropical ecosystem, hosting species that do not normally breed in, and are not commonly found anywhere else within, the continental United States or the islands and waters surrounding it.

[45] The park features the only nesting colonies of sooty tern, brown noddy, magnificent frigatebird, and masked booby in the contiguous United States.

[46] Birdwatching activity peaks each spring (usually April) when dozens of migratory bird species can pass through the park in a single day.

An active eradication program has resulted in the removal of invasive Casuarina trees and agave from Loggerhead Key, by cutting and herbicide treatment.