Fort Jefferson, Powder Magazine B, Garden Key, Key West, Monroe County, FL

Fort Jefferson was part of Fort Jefferson National Monument from 1935 to 1992. Since then it has been part of Dry Tortugas National Park. The address for the survey has been updated to reflect this change.
This survey originally used the name "Fort Jefferson, Powder Magazine B." Research by staff at Dry Tortugas National Park indicated that name was incorrect, so it was changed to "Fort Jefferson, Small Detached Magazine."
Significance: Located on the Parade Grounds to support the military functioning of Fort Jefferson were the Large and Small detached magazines, where the gun powder was to be safely stored. The Small Magazine was intended to serve as the powder storage facility secondary to the Large Magazine, both of which were supplemented by lesser magazines occupying two casemates of each long curtain wall and in each bastion tower. The Small Magazine utilized the innovated, shell-proof, barrel-vaulted brick arch and concrete construction for which its designer, Chief Engineer of the U.S. Army General Joseph Totten, was well known. According to the original specifications for Fort Jefferson, there were to be five independent or free-standing magazines two of which were to measure 48' x 28' and three, 30' x 28'. Instead, Large and Small magazines were built, with the later measuring 56-2"' x 64'-5" and 7'-6" in height. While about 20' smaller than the Large Magazine and including two vaults rather than four, it shares basic features.

Detailed instructions for the construction of the Small Magazine did not arrive at the fort until December 1861, however, following the start during the previous spring of the Civil War, when the fort witnessed its highest use. While Totten instructed work to begin immediately, the Small Magazine was not begun until after the war. The construction of the Small Magazine essentially mirrored that of the Large Magazine, lagging slightly behind. In June 1865, work began on the foundation of the Small Magazine as that of the Large Magazine was completed. Work continued between 1865 and 1870, although the Large and Small parade magazines were never truly finished. By 1876 they were no longer necessary and by 1891, all the fort's magazines were emptied of powder and munitions. Although structurally sound, the magazines show damage by weaponry fire.
Survey number: HABS FL-44-D
Building/structure dates: 1865-1870 Initial Construction
National Register of Historic Places NRIS Number: 70000069, 01000228