But a small group of coral reefs about 75 miles farther to the west actually mark the western terminus of the string of subtropical islands that jut southwestward from the bottom of the Florida peninsula.
Discovered by Ponce de Leon in 1513, the Dry Tortugas are called “dry” because they have no pools of fresh water. Tortugas is the name for turtles in the Spanish language.
The islands were created when coral formed a network of reefs above a rise of older limestone formations on the floor of the Gulf of Mexico.
The 10 tiny atoll-like islands are only accessible by boat or seaplane, and seven of them have been designated the Dry Tortugas National Park.
The photograph to the right was taken by an astronaut aboard the International Space Station when it passed over the Dry Tortugas on May 29, 2008.
Clearly visible are the walls of a Civil War-era garrison known as Fort Jefferson. Its extremely remote location was deemed a fitting place to imprison Dr. Samuel Mud, the doctor who set the broken leg of John Wilkes Booth following Booth’s assassination of President Abraham Lincoln in 1865. It was also used to house Union deserters during the Civil War.
Over sixteen million bricks were used to construct a perimeter fifty feet high and eight feet thick, making it the largest brick building in the Western Hemisphere. The fort is currently undergoing extensive restoration to prevent a collapse of the hexagonal outer walls.
