Antietam
In september of 1862 in maryland the union and the confederacy met along the Antietam creek McClellan led the union and lee led the confederates and they fought until both had heavy casualties. Lee retreated his troops back to virginia so the union declared it their victory but no one really won with the confederates suffering the loss of 2,770 out of 52,000 and another 11,000 more wounded or mising. the union suffered heavily too with 21,00 out of 75,000 dead and another 10300 wounded or missing. This sets the record for most american casualties in one battle. Outnumbering the deaths in the war of 1812 andthe mexican american war combined.