At 2 A.M., three of the overloaded steamboat’s boilers suddenly exploded. The blast blew gaping holes into the decks and killed hundreds instantly. “The explosion came with a report exceeding any artillery that I had ever heard, and I had heard some that were very heavy at Gettysburg,” Union Private Benjamin Johnston recalled. Hot coals rained down on the steamship, which erupted into a floating inferno.

Those unable to swim—which were most of the passengers—were forced to make split-second decisions between burning or drowning. The struggle to stay alive became a survival of the fittest among a bunch of very unfit men. Already weakened passengers desperately fought the strong currents and exposure as they clung to wooden debris, mattresses and the charred carcasses of army mules floating in the freezing river. As soon as Sultana’s sole lifeboat hit the Mississippi, dozens of flailing men clawed to climb aboard, and the collective weight took all of them down to the river’s murky bottom. A soldier even attacked a woman in an attempt to rip off her life belt. “The animal nature of man came to the surface in the desperate struggle to save himself regardless of the life of others,” wrote Union Private John Walker.

For days afterward, rescuers plucked bodies from trees near the blast zone and pulled them from the river as far south as Vicksburg, 200 miles away. Historians believe that more than 1,800 of the paddle wheeler’s passengers perished. Although called “America’s Titanic,” the Sultana disaster actually claimed 300 more lives than the famed 1912 shipwreck and still remains the greatest maritime disaster in American history.