Sept 17th 1862. The bloodiest day in US History. Of the 23,000 casualties, 3600 were dead. And we all know that back in that era, a significant number of the wounded would linger on for weeks or months till they too died. General McClellan's handling of the battle was horrible. He could have won the battle early on (and wiped out General Lee while doing it) just by handling some basic staff work prior to the fight.