In the summer of 1864, residents of Elmira, New York, could pay 10 or 15 cents to climb a wooden observation tower, buy snacks, and look down into a Union prison camp the inmates called Hellmira. This episode traces how Camp Rathbun, a Union training depot at the junction of the Erie Railroad and the Northern Central Railway, became one of the deadliest prisoner of war camps in the North after the Dix-Hill cartel collapsed over the Confederacy’s treatment of captured Black Union soldiers. Commissary General of Prisoners William Hoffman gave Lieutenant Colonel Seth Eastman 10 days to prepare for 10,000 prisoners, though Eastman warned the camp could hold perhaps half that, with kitchens for 5,000 and no hospital.

Within a month the camp built for about 4,000 men held 12,000. Latrines drained into the stagnant Foster’s Pond, surgeon Charles T. Alexander’s warning went unheeded by the cost-conscious Hoffman, and rations were cut in retaliation for reports from Andersonville. In the winter of 1864 to 1865, with temperatures at 18 below zero, many prisoners lived in canvas tents. By the time the camp closed, 2,970 men had died, a mortality rate of 24.5 percent. The episode also follows the formerly enslaved sexton John W. Jones, who buried the dead at Woodlawn Cemetery, and the postwar effort to dismiss the camp’s record.

• On July 15, 1864, a train carrying more than 800 prisoners collided head on with a coal train near Shohola, Pennsylvania, killing 49 prisoners and 17 Union guards.
• Starving prisoners caught and ate rats, which became a form of currency inside the camp.
• Only 10 men ever escaped, including Washington B. Traweek, who held out in a sweat box rather than name the tunnelers to commandant Henry V. Colt, brother of Samuel Colt.
• John W. Jones, who escaped slavery in Virginia in 1844, kept records so precise that only seven of nearly 3,000 graves are marked unknown.
• The camp was dismantled, its lumber sold and the land farmed, and reconstruction efforts at the site began in 2015.