What Was the Deadliest Single Day Battle in American History?

The Civil War, fought between 1861 and 1865, remains the deadliest conflict in American history with a staggering death toll of more than 620,000. It was a war that divided the nation and pitted brother against brother. The Battle of Antietam, which took place on September 17, 1862, was the single deadliest day in American military history.

The Battle of Antietam

The Battle of Antietam was fought near Sharpsburg, Maryland, and was the culmination of Confederate General Robert E. Lee’s Maryland Campaign. Lee’s army had crossed into Maryland to gather supplies and recruit fresh troops. Union General George B. McClellan pursued Lee’s army and caught up with them near Antietam Creek.

The Battle

The battle began at dawn on September 17 when Union soldiers attacked a Confederate division commanded by General Thomas J. “Stonewall” Jackson. The fighting quickly spread to other parts of the battlefield as both sides brought in reinforcements.

The battle raged for hours with neither side gaining a decisive advantage. The fighting was intense and brutal as soldiers fought hand-to-hand with bayonets and clubbed muskets.

By mid-afternoon, General Ambrose Burnside led his Union troops across a stone bridge over Antietam Creek and attacked the Confederate right flank. The Confederates were pushed back but managed to hold their ground.

As night fell, both sides were exhausted and had suffered heavy casualties. More than 23,000 Americans were killed or wounded on that single day of fighting.

The Aftermath

Although it was not a clear-cut victory for either side, the Union Army held the field at the end of the day. Lee’s army withdrew across the Potomac River into Virginia shortly after the battle.

The Battle of Antietam was a turning point in the Civil War. It gave President Abraham Lincoln the opportunity to issue the Emancipation Proclamation, which declared that all slaves in Confederate-controlled territory were to be freed.

  • More than 3,600 Union soldiers died at Antietam.
  • Over 2,700 Confederate soldiers were killed.
  • The total number of casualties was over 23,000.


The Battle of Antietam was a brutal and deadly conflict that changed the course of American history. It remains a reminder of the sacrifices made by so many Americans in the pursuit of freedom and unity.