The Battle of Shepherdstown, also known as The Battle of Boteler's Ford, took place September 19–20, 1862, in Jefferson County, Virginia (now West Virginia), at the end of the Maryland Campaign of the American Civil War. With almost 700 killed this would be the bloodiest battle ever fought on WV soil.
The Battle of Shepherdstown convinced both army commanders that the Maryland Campaign was over. On the Union side, McClellan saw that an aggressive pursuit of the enemy into Virginia was not an option. The engagement at Shepherdstown forced Lee to rethink, and ultimately abort, his efforts to reenter Maryland. With the Confederate army effectively driven from Northern soil, President Abraham Lincoln used the opportunity to claim a Union victory, and on September 22, 1862, he issued the preliminary Emancipation Proclamation.
Source: McGrath, Thomas "Battle of Shepherdstown." e-WV: The West Virginia Encyclopedia. 20 September 2016.