No. The total casualties on the Union side came to 2,010 killed, 9,416 wounded, and 1,043 missing, for a total of 12,469. Confederate losses are harder to be named with certainty, partly because there had been so many desertions, but it was at least equal to the Northern loss. Therefore, we can say, with little hesitation, that roughly 25,000 Americans were killed, wounded, or went missing in one day’s battle. Let us compare that to other terrible days in American history.

On December 7, 1941, 2,386 Americans died when the Japanese bombed Pearl Harbor. That was indeed a black day in American history, but it did not come close, either in relative or in absolute terms, to the blood that flowed at Antietam. On September 11, 2001, 2,996 Americans were killed in the immediate aftermath of the terrorist attacks on the World Trade Center in New York City. While it was a horrific scene, and day, it does not approach the losses at Antietam. And even at the height of the Second World War, when the United States fought on two fronts—the battle-hardened Germans on one and the fanatical Japanese on the other—there was no day in which the casualty number or percentage came even close.

Antietam stands alone.