America's bloodiest day" - the Battle of Antietam on September 17, 1862 - left more dead American soldiers in its wake than any other 24-hour period in history. Antietam and the related battles of the Maryland Campaign that led up to the lethal confrontation did not result in decisive defeats for either side. But they did serve as a brutal warning to an out-gunned, out-commanded, and out-organized Union army. This guide will be invaluable to anyone - from battlefield explorer to armchair observer - who wants a moment-by-moment replay of one of the most significant Civil War campaigns.