The Battle of Antietam was the first major combat of the Civil War that occurred in northern territory. The battle took place on September 17, 1862, near Sharpsburg, in Washington County, Maryland, United States, and in the vicinity of the Antietam stream. The battle was part of the Maryland Campaign and is the bloodiest in the history of the United States that was fought in a single day, with almost 23,000 casualties.
The Battle of the Antietam is considered a missed opportunity for the Union to inflict a devastating blow on the Northern Virginia Army and prematurely end the Civil War.
At the same time, its outcome was a strategic victory for the Union, politically considered by many historians to be one of the most important turning points in the war. It opened up the possibility for Lincoln to announce his Emancipation Declaration, which undermined attempts by Great Britain and France to negotiate a peace agreement, and helped the Republican Party to avoid impending defeat in the 1862 congressional elections.