Fort Delaware: Confederate Hellhole
Delaware City, Delaware
Fort Delaware stands on Pea Patch Island in the Delaware River. It's a castle-like fortress surrounded by a moat. Originally built to protect Wilmington and Philadelphia, it became infamous during the Civil War as a jail for Confederate POWs. 33,000 were imprisoned, nearly 2,700 died from dysentery, scurvy, and smallpox (They're buried in a mass grave in New Jersey).
Summer days can still be as miserably hot and humid at the fort as they were in 1864, but today's tourists and costumed "living history" interpreters at least escape the medical maladies of yore. In September and October there are Haunted Fort tours, and every year in May the "Escape from Fort Delaware Triathlon" is run along the same path used by the Fort's 52 Civil War prisoners who managed to break out and swim across the river.