Wikimedia
Wikipedia: Battle of Antietam
This Wikipedia article on the bloodiest battle in American history gives background information on the battle, the battle itself, and the aftermath.
Curated OER
National Park Service: Antietam National Battlefield
The National Park Service offers a wealth of information on Antietam, the battle, casualties, flags, and weapons. A very worthwhile site.
Other
Antietam on the Web
A comprehensive resource from Antietam on the Web of the Battle of Antietam, including historical documents, battle maps and much more.
American Battlefield Trust
American Battlefield Trust: Civil War: Battle of Antietam: Facts & Summary
A large collection of resources for learning about the Battle of Antietam.
PBS
Pbs Teachers: Conflicting Newspaper Accounts (Civil War Lesson Plan) [Pdf]
Multilayered lesson plan that begins with analysis of a series of photographs of the battle of Antietam and ends with writing an account of the battle in the style of a nineteenth-century war correspondent from opposing perspectives of...
Independence Hall Association
U.s. History: Bloody Antietam
Read an account of the battle of Antietam and the tactical mistakes of the tentative General George McClellan. The bloodiest battle of the Civil War brought about many changes.
Curated OER
National Park Service: Cwsac: Civil War Battle Summaries: Battle of Antietam
This site, which is provided for by the National Park Service, gives a brief overview of the events at the Civil War Battle of Antietam.
Other
Civil War Album: Site Photos: Battle of Harpers Ferry
A brief description of the attack on Harpers Ferry along with maps of Confederate troop placements and photos of how it looks today.
Ohio State University
E History at Osu: Maps & Images: Antietam
Images of the Battle of Antietam. Shows the landscape of the battlefield as well as images during and the aftermath of the battle.
Library of Congress
Loc: America's Story: The Battle of Antietam
What was the bloodiest battle in all American history? The Battle of Antietam , during the Civil War, wins this dubious honor. The Library of Congress has more information about this famous battle along with some actual photographs.