According to many historians, the single bloodiest day of the Civil War was September 17, 1862, when General George McClellan’s Union forces and Robert E. Lee’s Confederate troops clashed in the Battle of Antietam.
The savage struggle took place at Antietam Creek near Sharpsburg, Maryland, ending with the retreat of Lee’s army into Virginia on September 18.
The Union suffered over 12,000 casualties, with 2,100 men killed; the Confederates suffered over 10,000 casualties, with 2,700 men killed.