The hundreds of Union veterans and recently released prisoners of war who boarded the steamboat Sultana on April 24, 1865, were bloodied, exhausted and starving—but unlike more than 600,000 of their fellow soldiers who fought in the Civil War, they were alive. They had survived barbarous battles and notorious POW camps such as Andersonville and Cahaba. Most of them, however, would not survive the seemingly routine trip home.

As the soldiers boarded the giant wooden steamship docked in Vicksburg, Mississippi, some of them heard hammering in the engine room where furious repairs were being made to one of the vessel’s four coal-fired boilers, which had begun to leak on the journey up the Mississippi River from New Orleans. Vicksburg boilermaker R.G. Taylor, who had been summoned to the ship, found a bulge in a seam and told Sultana’s captain and part owner, J. Cass Mason, that a proper repair would take days.

For Mason, however, time was indeed money. During the Civil War, the War Department contracted with private steamboat operators to transport troops—paying $5 for every enlisted man and $10 for each officer. Not wanting to miss out on a big payday, Mason ordered Taylor and his crew to place a temporary patch on the leaky boiler and vowed to make full repairs once his steamer reached its destination in Cairo, Illinois.

Steamboat captains weren’t above bribing military officials to steer passengers to their ships, and Reuben Hatch wasn’t above taking them. The Union Army’s chief quartermaster in Vicksburg, who oversaw the contracting of private steamboats, had been court-martialed for graft in 1861, but his brother, Illinois Secretary of State Ozias Hatch, had the ear of President Abraham Lincoln, who interceded to have the charges dropped. Although a February 1865 government examining board had found Hatch “totally unfit” to serve as quartermaster, his powerful political connections kept him protected.

Likely incentivized by a kickback from Mason, Hatch steered 2,400 passengers onto Sultana, which was licensed to carry only 376 passengers, while two other steamboats sat in Vicksburg practically empty. “We were driven on like so many hogs until every foot of standing room was occupied,” Union Corporal George M. Clinger recalled. So many passengers piled aboard the wooden-hulled steamboat that its decks began to sag until the crew hastily reinforced them with beams to prevent their collapse. When Sultana reached Helena, Arkansas, the rush of soldiers to one side of the ship to pose for a photographer nearly capsized the vessel.

After the crew unloaded 250 barrels of sugar and 97 cases of wine in Memphis, the steamboat became particularly top-heavy. Still carrying six times its legal capacity, Sultana wobbled against the currents of the flood-swollen Mississippi in the early morning hours of April 27. Given the flood conditions and the weight of the passengers, the boilers strained as the careening ship paddled upriver.

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.

Unlike the Titanic sinking, however, the Sultana tragedy quickly faded into historical obscurity. Reports of Sultana’s sinking were overshadowed by news the day before that Confederate General Joseph Johnston had agreed to the Civil War’s largest surrender as well as the end of the manhunt for John Wilkes Booth, the man who had assassinated Abraham Lincoln two weeks earlier.

Andrew Carroll, who wrote about Sultana in his book “Here Is Where: Discovering America’s Great Forgotten History,” says the monstrous loss of life also lost any shock value to a public already numbed by the Civil War’s unfathomable body count. “There were battles in which tens of thousands of soldiers were casualties, so, to be honest, losing 1,800 wasn’t seen as much more horrific.”

“We have as a people become so accustomed to suffering of horrors during the past few years that they soon seem to lose their appalling features, and are forgotten,” the Memphis Argus reported just 11 days after the tragedy. “Only a few days ago 1,500 lives were sacrificed to fire and water, almost within sight of the city. Yet, even now, the disaster is scarcely mentioned—some new excitement has taken its place.”

Conspiracy theorists suspected Confederate spies had planted bombs on board the steamboat as an act of sabotage, but the leaky boilers were likely to blame. The overcrowding resulted in the incredible death count, if not the explosion itself by overtaxing the weakened boilers. Three separate commissions investigated the disaster but ultimately held no one responsible. Hatch ignored three subpoenas and was never prosecuted. Mason went down with his ship.

Carroll notes that many of the victims, even in death, suffered further indignity. In 1867, the military disinterred victims from their initial graves so that they could be reburied with military honors in Memphis National Cemetery. The military chalked the names of the men on their caskets, but a thunderstorm erupted en route and washed away the identities of the deceased, who are now buried in row after row of unmarked graves.