On September 17, 1862, George B. McClellan’s Army of the Potomac attacked Robert E. Lee’s Army of Northern Virginia between Antietam Creek and the Potomac River outside Sharpsburg, Maryland. At the end of the day, 23,000 Americans were dead, wounded or missing—still the greatest single-day casualty total in America’s history.

In this short video presentation, park rangers from the Antietam National Battlefield Park describe the day’s events.