The story
Fort Jefferson commands Garden Key in Dry Tortugas National Park, seventy miles west of Key West, Florida — the largest masonry structure in the Americas, sixteen million bricks raised from 1846 to guard the Gulf shipping lanes, never finished and never attacked, but famous as the military prison that held Dr. Samuel Mudd, convicted in the Lincoln assassination conspiracy for setting Booth's leg; Mudd's heroism nursing the fort through its 1867 yellow fever epidemic — which killed the post surgeon and dozens of the garrison, dead this record honours — won his pardon, and his cell is the park's most visited chamber. Reached by ferry or seaplane, the fort hosts day visitors and a primitive campground whose overnighters supply the telling: a sentry's figure on the moonlit ramparts, footsteps in the casemate arcades, voices and coughing from the old hospital sections, lights in the officers' quarters — undocumented, isolation-flavoured, traded around campfires seventy miles from anywhere. Present Fort Jefferson as engineering-and-imprisonment heritage first, its rampart sentries the reef's remotest lore. Park logistics from NPS pages.