Battle Of Antietam: The Second Deadliest Day In American History

"The Battle of Antietam - Army of the Potomac, General George B. McClellan, commander, September 17, 1862," color lithograph, unknown artist, 1888, published by Kurz & Allison, Art Publishers, Chicago. (VCG Wilson/Corbis via Getty Images)

When 3,650 people died on September 17, 1862, it became the single deadliest day in American military history and the second deadliest day the country has ever seen at all, just behind the Galveston hurricane of 1900. The Battle of Antietam, also called the Battle of Sharpsburg, turned the tide of the American Civil War, in part due to the staggering number of casualties and in part thanks to the new technology of photography that brought the horrors of the battlefield to newspapers across the country. While the Battle of Antietam was a key moment in the Civil War, it was also an event filled with missed opportunities.

Both Sides Needed The Win

The Union Army assumed that victory over the Confederacy would be swift and easy, but as summer 1862 wore on, it became clear that the Southern states were a formidable foe. The Confederacy hammered this home with their defeat of Major General John Pope and the Union troops at the Second Battle of Bull Run. President Abraham Lincoln had his Emancipation Proclamation ready to announce, but he knew it would carry much more weight if it came on the heels of a decisive Union victory.

To make matters worse, Lincoln was facing a mid-term election that threatened to flip control of Congress from Lincoln's Republicans to the anti-war Democrats. Confederate General Robert E. Lee was well aware of this, of course, and hoped a few more Union defeats might swing the mid-term election to the Democrats, thus yanking Lincoln's congressional support.