Often referred to as "the bloodiest single day battle in U.S. history," the Battle of Antietam was also the first major engagement of the Civil War to take place north of the Mason-Dixon. From Wikipedia:
After pursuing Confederate General Robert E. Lee into Maryland, Union Army Maj. Gen. George B. McClellan 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.
By nightfall, 23,000 people had died.
P.S. Naming your stupid football game after one of the most harrowing, divisive, and murderous chapters of U.S. history is like naming a hopscotch tournament, "The Trail of Tears." Or... "9/11 dodgeball game," anybody?