Fort Warren is a granite coastal fort on Georges Island in Boston Harbor, built roughly 1833–1861. In the Civil War it held Confederate prisoners, officers, and political detainees — among them Confederate Vice President Alexander H. Stephens. The post stayed in military use into the twentieth century and is now a National Historic Landmark within the Boston Harbor Islands park system.

The legend: a Confederate prisoner’s wife (often named Melanie Lanier; husband variously Andrew or similar) learns he is held at Warren, reaches Hull, crosses to the island in disguise (sometimes with pick and pistol), is discovered during an escape attempt, accidentally kills her husband when a weapon misfires, and is hanged as a spy after requesting to die in women’s mourning dress — soldiers supply black cloth (sometimes said to be curtains), hence “Lady in Black.” Her spirit is then reported in corridors, casemates, arches, and prison areas: a dark-clad woman, footsteps, female voices or cries.

Historical checks have not produced widely accepted primary evidence for that woman, the infiltration, or a female hanging at the fort. Military executions leave paper; a woman’s execution inside a Union prison would be extraordinary. A real Confederate prisoner named Samuel Lanier did die at Fort Warren in January 1862 (smallpox in secondary accounts) — a grain of truth later tellings may have embroidered. The story’s modern shape is strongly tied to folklorist Edward Rowe Snow, who printed it in The Romance of Boston Bay (1944) with the open caveat that he offered the legend “without the slightest guarantee that any part of it is true,” and who used costumed “Lady” jumpscares on lantern tours while campaigning to save the fort.

Visitor and investigator reports of dark figures, sounds, and EVPs continue; stone acoustics and expectation also explain many experiences without a ghost.