The correct answer is Antietam. The Battle of Antietam, fought on September 17, 1862, in Maryland, was the first major battle in the American Civil War to take place on Union soil. The Union Army, led by General George McClellan, achieved a tactical victory over Confederate General Robert E. Lee's Army of Northern Virginia. It is considered a significant victory for the Union because it forced Lee to retreat and it gave President Abraham Lincoln the opportunity to issue the Emancipation Proclamation.
