SHARPSBURG, Md. (AP) -- Pulitzer Prize-winning historian James McPherson leads the lineup of speakers marking the 150th anniversary of the Civil War Battle of Antietam near Sharpsburg, Md.
The midday ceremony at the battlefield caps a long weekend of lectures, hikes and other events devoted to the bloodiest day of combat on U.S. soil.
McPherson has written that Antietam was arguably the most important battle of the war.
More than 23,000 men were reported killed, wounded or missing there on Sept. 17, 1862. Their sacrifices enabled President Abraham Lincoln to announce his preliminary Emancipation Proclamation five days later.
The battle was inconclusive but the Confederates retreated to Virginia the next day. Had the South prevailed, France and England were prepared to recognize the Confederacy as a separate nation.