What was an effect of the Battle of Antietam?
The Confederacy lost greatly.
The Battle of Antietam was the first battle of the Civil War where Confederate general Robert E. Lee invaded the Union. Antietam is a town in Maryland. September 17, 1862 was the single most bloodiest day in American history. The Confederacy lost so many soldiers that they didn't come back for a long time in the war. The Union won that battle. Also, after that battle, Union general George McClellan was fired by commander-in-chief Abraham Lincoln. Mister McClellan was a terrible general.
One effect of the Battle of Antietam was the Proclamation of Emancipation.
Abraham Lincoln had wanted to issue the Proclamation of Emancipation turning the Civil War into a battle not only to preserve the union but also to abolish slavery.
The Union had lost every major battle up the battle of Antietam. Abraham Lincoln did not want to issue the Proclamation of Emancipation from a position of weakness. To issue the Proclamation after a Union defeat would seem as act of desperation and would weaken the effect of the Proclamation.
The victory at the battle of Antietam gave Abraham Lincoln a platform to issue the Proclamation from a position of strength. This changed the character of the Civil War and prevented the European powers from intervening on behave of their trading partners of the southern Confederacy.