Most importantly, Union victory at Antietam provided President Abraham Lincoln the opportunity he had wanted to announce the Emancipation Proclamation, making the Battle of Antietam one of the key turning points of the American Civil War.

The important about the Battle of Antietam was the Union victory.

Antietam, the deadliest one-day battle in American military history, showed that the Union could stand against the Confederate army in the Eastern theater. It also gave President Abraham Lincoln the confidence to issue the preliminary Emancipation Proclamation at a moment of strength rather than desperation.