In 1846, the United States began building a fort for the coastal defense of Florida. Fort Jefferson, the largest masonry fort in the United States, took up just about all the space on 25 acre Garden Key, located in the Dry Tortugas-a chain of tiny sun-bleached islands west of Key West.
Climate on the barren sand was horrible: the sun beat down mercilessly and the humidity fostered mildew and rot. Swarms of flies, mosquitoes, and gnats plagued the islands. There was no water, no trees-nothing but sand, and that rose only three feet above the sea. Every item needed for construction and for support of the workers had to be imported. By late 1861, with the fort's half mile of 50 foot high brick walls still under construction, the federal government decided to use the facility as a prison. Not intended to confine Confederate prisoners of war, the fort was used instead as a dumping ground for criminals from Union armies.
Maj. Gen. George B. McClellan sent 63 rebellious soldiers from the 2d Maine Infantry to spend the war toiling on the desolate dot of sand. One of the worst Union prisons in the Civil War, the fort had a well deserved reputation as America's Devil's Island. A sentence to hard labor at Fort Jefferson was a sentence in hell. The unending job of construction, usually while wearing a ball and chain, a diet of tainted, diarrhea-and scurvy-causing food, swarms of insects, bedbugs, isolation, brutal guards, and plagues of yellow fever and malaria all combined to make life intolerable and uncertain.
Unimportant to the Confederate war effort, Fort Jefferson was 1 of 4 U.S. forts in the Deep South that escaped capture by the Confederates at the beginning of the war.