On September 17, 1862, an epic battle erupted along the banks of Antietam Creek, near the small Maryland town of Sharpsburg. Here the Union Army of the Potomac - Major General George B. McClellan commanding - and the Confederate Army of Northern Virginia - Robert E. Lee commanding - clashed for 12 straight hours. The battle itself can be divided into three different phases: the Cornfield, the Bloody Lane, and the Burnside Bridge.

The opening phase of the battle took place in a head high cornfield owned by a farmer named Miller. Here and in the areas immediately around it, some of the bloodiest and most intense action of the Civil War would take place as elements of three different Union army corps attempted to wrestle control of the area from troops under the command of Stonewall Jackson. In just 4-5 hours of combat, the two armies would suffer a combined 12,000 casualties in this sector with the Cornfield changing hands no less than 10 different times. While the fighting on this part of the field was desperate, it also turned out to be completely inconclusive as both sides simply fought themselves to exhaustion. From here the battle would shift south to a sunken wagon road that would hereafter be known as the Bloody Lane.

The Confederate center had taken shelter in the Bloody Lane, which they hoped to use as a natural trench against oncoming Federal attacks. Two separate Union divisions would strike at the Confederates in this area, the first of which was heavily mauled by the Rebel defenders. The second division, that of Israel Richardson, managed to get up close and flank the Confederate position. A mistaken order to retreat, however, sent the Confederates falling back toward Sharpsburg - a move that cracked Lee's center wide open. Small but ferocious counterattacks by troops organized by Confederate general James Longstreet kept the Federals at bay. Upon hearing of the success of his soldiers at the Bloody Lane, McClellan was asked if he wanted to commit his reserves to the fight. He erred on the side of caution, however, and kept the thousands of men he had at his disposal from exploiting the breach. The brief firefight at the Bloody Lane had been a violent one, with both sides suffering a combined 5,600 casualties. Antietam's battle toll was now 17,500 and climbing...

As the battle for the Bloody Lane cooled down, the fighting shifted south once again to a stone bridge spanning Antietam Creek. Here 12,500 men under the command of Major General Ambrose Burnside were being kept from crossing the Antietam by some 400 Georgians under the command of Colonel Henry L. Benning. Burnside wasted precious time in his attempts to cross the bridge which now bears his name, taking three hours to storm and capture the span. Burnside then wasted another three hours crossing his IX Corps across the Antietam and getting them into battle formation. He began his assault around 3 PM, with just 3,000 Confederates standing between him and Robert E. Lee's escape route back to Virginia. The inexcusable time it took to take the Burnside Bridge and to organize his men for a final assault came back to haunt him, however. Just then, A.P. Hill's Light Division was arriving on the field after a forced march from Harpers Ferry. They slammed right into the left flank of Burnside's assault force and forced it to retreat back to the Burnside Bridge in disarray.

As night fell the fighting along Antietam Creek began to die down. The next day, September 18, Lee remained in his position daring McClellan to attack him. McClellan, however, refused to do so and Lee retreated back into Virginia that evening. Tactically, the Battle of Antietam was a stalemate but strategically it was a Northern victory as Lee was forced to abandon his Maryland campaign. Lincoln used this opportunity to announce his Emancipation Proclamation on September 22. Dissatisfied with McClellan's failure to follow up and pursue Lee's army in the battle's aftermath, Lincoln would permanently relieve him of command two months later.

In one day, more than 3,600 men were killed and 19,000 were wounded and captured - more American dead than Pearl Harbor, D-Day, or 9/11. Shocking portraits of the dead at Antietam, taken by photographer Alexander Gardner, are displayed in the North - bringing the horrors of war to a curious public for the very first time.

September 17, 1862, remains the bloodiest single day in American history.