A Ku Klux Klan group plans to hold a rally June 10 on the grounds of the Antietam National Battlefield, site of the bloodiest one-day clash of the Civil War, an organizer and a park official said.

Battlefield Superintendent John W. Howard said Tuesday the National Park Service approved the white supremacist group's application for a permit to use the park to exercise its free speech rights.

"It would be very difficult to find a reason why a First Amendment permit would be denied," Howard said.

Gordon Young, Imperial Wizard of the World Knights of the Ku Klux Klan, estimated in his application that about 100 people would attend the rally at the nearly 3,300-acre park.

Howard said the park service would establish separate areas for news media and counter-demonstrators. Park Service police would be aided by state and local law enforcement in providing security, he said.

Nine Klan members marched in an event the group held in nearby Sharpsburg in 2004. Young, of Hagerstown, said at the time that he chose to rally in Sharpsburg partly because of its proximity to Antietam, to honor fallen Confederate soldiers.

On Sept. 17, 1862, more than 23,000 men on both sides were killed, wounded or reported missing at the western Maryland battlefield.

The Confederacy's failure to achieve a clear victory at Antietam gave President Lincoln the political strength to issue the Emancipation Proclamation freeing slaves in the South.