<Ul> <Li> Mile Hill </Li> <Li> Harpers Ferry </Li> <Li> Crampton's Gap </Li> <Li> South Mountain </Li> <Li> Antietam </Li> <Li> Shepherdstown </Li> <Li> Chambersburg Raid </Li> <Li> Unison </Li> </Ul> <Li> Crampton's Gap </Li> <P> The Battle of Antietam / ænˈtiːtəm /, also known as the Battle of Sharpsburg, particularly in the Southern United States, was a battle of the American Civil War, fought on September 17, 1862, between Confederate General Robert E. Lee's Army of Northern Virginia and Union General George B. McClellan's Army of the Potomac, near Sharpsburg, Maryland and Antietam Creek . Part of the Maryland Campaign, it was the first field army--level engagement in the Eastern Theater of the American Civil War to take place on Union soil . It was the bloodiest day in United States history, with a combined tally of 22,717 dead, wounded, or missing . </P> <P> After pursuing the Confederate general Robert E. Lee into Maryland, Maj. Gen. George B. McClellan of the Union Army launched attacks against Lee's army, in defensive positions behind Antietam Creek . At dawn on September 17, Maj. Gen. Joseph Hooker's corps mounted a powerful assault on Lee's left flank . Attacks and counterattacks swept across Miller's Cornfield, and fighting swirled around the Dunker Church . Union assaults against the Sunken Road eventually pierced the Confederate center, but the Federal advantage was not followed up . In the afternoon, Union Maj. Gen. Ambrose Burnside's corps entered the action, capturing a stone bridge over Antietam Creek and advancing against the Confederate right . At a crucial moment, Confederate Maj. Gen. A.P. Hill's division arrived from Harpers Ferry and launched a surprise counterattack, driving back Burnside and ending the battle . Although outnumbered two - to - one, Lee committed his entire force, while McClellan sent in less than three - quarters of his army, enabling Lee to fight the Federals to a standstill . During the night, both armies consolidated their lines . In spite of crippling casualties, Lee continued to skirmish with McClellan throughout September 18, while removing his battered army south of the Potomac River . </P>

What was the first major battle of the civil war to be fought on union soil