The bloodiest day in American history takes place as the armies of Robert E. Lee and George B. McClellan fight to a standoff near Sharpsburg, Maryland, along Antietam Creek.
Letter from David Ash, Company B, 37th Illinois Volunteer Infantry, three days after the Battle of Pea Ridge.
Henry H. Sibley’s Confederate Army of New Mexico begins its mission to conquer the New Mexico Territory, culminating in a fight for a ford on the Rio Grande.
Federals score their greatest victory of the war up to this time, generating a new national hero in the process.
The year closes with southerners optimistic about gaining independence and northerners pessimistic about preserving the Union.
Federal forces suffer another horrific defeat when they are driven off a cliff overlooking the Potomac River at Leesburg, Virginia.