Battle of Antietam.
Official or not, many of the battles had different name by the Confederates. The Confederates usually named a battle with a nearby town and the Union would name it for the nearest river or other topographical feature.
Antietam is a creek near Sharpsburg, MD. The Confederate name for the battle is Sharpsburg.
The Battle of Sharpsburg
Antietam
Known to the Confederacy as Sharpsburg.
The Confederates called Antietam the Battle of Sharpsburg.
The Battle of Antietam (Battle of Sharpsburg) .
The Battle of Antietam was known as Sharpsburg to the Confederate forces.
The alternative name was the Battle of Sharpsburg. Both are reasonably good names: the battle was mainly fought in the area between the town of Sharpsburg and Antietam Creek.
The battle at Sharpsburg was named Antietam after nearby Antietam Creek. Southerners prefer to call it The Battle of Sharpsburg.
Antietam Creek, near Sharpsburg, Maryland.
The Battle of Antietam (or Sharpsburg) was sometimes called the Confederate High Watermark, because it was when they came nearest to achieving foreign recognition as a viable nation. But they unexpectedly lost the battle, and along with it, they lost momentum generally. The following July, the simultaneous struggle for Gettysburg and Vicksburg was also described as the Confederate High Watermark, though recognition was much less likely by then.
Battle of Sharpsburg