|Battle of Antietam, as depicted in Battle Cry -- 150th Anniversary Edition|
It's hard to believe, really, given the traumas of the 20th Century, not to mention 9/11, but the bloody field of Antietam, 150 years ago today, remains the day with the worst loss of American life due to violence in our history.
Battles are messy affairs by nature, and the Nineteenth Century was lacking in the comprehensive sort of accounting that we got used to in the 20th Century, so we can't be certain of the precise total losses. My 1984 Time-Life book on the battle lists at least 22,726 total casualties with at least 2,108 slain federals and 1,546 Confederates. The U.S. Army War College Guide to the Battle of Antietam lists slightly different figures taken from the Official Records of 2,010 Union and 1,567 Rebel dead. Perhaps 2,000 of the wounded later died and it's probable that many of those listed as missing from both sides were also killed.
While not the crushing victory promised by McClellan ("Here is a paper with which if I cannot whip Bobbie Lee, I will be willing to go home." he said, after getting a copy of Lee's campaign orders) or expected, given the nearly 2 to 1 edge in manpower, it was close enough for government work -- in this case the government work of issuing the Emancipation Proclamation.
Lincoln had been planning on the move for some time, but was waiting for a Union victory in the field to provide the proper backdrop. Antietam sufficed. While not destroyed, Lee was forced to retreat and his invasion of the North repulsed.
The Emancipation Proclamation was a monumental turning point in the war, even though it didn't actually free very many slaves. But it did represent a turning point, a fork in the road, on the subject of slavery. In the wake of the EP there was no turning back. Only a Southern victory would preserve the peculiar institution anywhere and even if the Union were defeated, it would be eliminated somewhere. There was no going back to the antebellum status quo.
In that sense, Antietam was a far more consequential battle than might be expected, purely on its battlefield results, which was basically a bloody stalemate.