page_title: Fort Jefferson (Florida)
section_title: Design
hierarchical_section_title: Fort Jefferson (Florida) / History / Design
caption_attribution_description: Interior wall, parade ground, and harbor light of Fort Jefferson, the Dry Tortugas
context_page_description: Fort Jefferson is a massive but unfinished coastal fortress. It is the largest brick masonry structure in the Americas, and is composed of over 16 million bricks. The building covers 16 acres. Among United States forts, only Fort Monroe in Virginia and Fort Adams in Rhode Island are larger. The fort is located on Garden Key in the lower Florida Keys within the Dry Tortugas National Park, 68 miles west of the island of Key West. The Dry Tortugas are part of Monroe County, Florida, United States.
context_section_description: The design called for a two-tiered casemates in a six-sided outline, with two curtain walls measuring 325 feet (99 m), and the other four measuring 477 feet (145 m). Corner bastions, which are large projections designed to allow defensive fire along the faces of the walls they joined, contained gunrooms, gunpowder magazines and a granite spiral staircase. Each tier of casemates contained 150 guns, and another 150 were placed on top of the fort itself. The heavy guns were mounted inside the walls in a string of open casemates, or gunrooms, facing outward toward the sea through large openings called embrasures. The 13-acre (5.3 ha) parade ground contained additional powder magazines, headquarters, a hospital, officer quarters and three large barracks.
  The Army employed civilian carpenters, masons, general laborers, and Key West slaves to help construct the fort. By August 1855, 233 white contract laborers were employed, though the slaves "... were the backbone of the labor gang ...," according to Albert Manucy. Bricks were provided by the Pensacola firm of Raiford and Abercrombie. In 1859, the scientist Joseph Bassett Holder assumed responsibility as the fort's physician.
  In order to support such a large population in an area lacking fresh water, an innovative system of cisterns was built into the walls of the fort. Sand-filled columns were placed at regular intervals in the inner walls, spanning their height from the roof to the foundation. The columns were intended to filter rainwater from the rooftop for long-term storage in a series of underground chambers. However, the rainwater dissolved salts in the sand, or the cisterns had not been made tight, making the water unfit for drinking, but usable for washing and cooking. Only the rainwater runoff stored under the parade ground was fresh for drinking. Two steam condensers distilled 7,000 US gallons (26,000 l) of sea water per day during the Civil War. The fort enjoyed "... much better water than we have had heretofore," which was stored in the parade ground cisterns.
caption: Interior wall, harbor light, and parade ground (2005)
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