The Battle of Antietam was the bloodiest day in American history, with a combined tally of 22,717 dead, wounded, or missing.
The battlefield itself is a National Battlefield and comes under the U.S. National Park Service.
It is extremely well preserved and looks very much like it did in 1862.
The Union called the battle Antietam after the creek that ran through part the of the battlefield, the Confederacy the name of the battle was “Sharpsburg”.
The Union forces frequently named battles for bodies of water or other natural features that were prominent on or near the battlefield, but Confederates most often used the name of the nearest town or artificial landmark.