GETTYSBURG - For almost a century, the small, historic stone house on Chambersburg Road has been obscured by the commercial buildings surrounding it.

But in 1863, it occupied a prominent position at the epicenter of fighting on Day One of the nation's best-known Civil War battle. That night, it would be seized and used as the headquarters of Confederate Gen. Robert E. Lee.

On Tuesday - exactly 151 years after the start of the Battle of Gettysburg - the Civil War Trust will announce the purchase of the four-acre parcel and the restoration of the site to the way it looked in 1863.

"As far as preserving a historically significant structure and part of the battlefield, this is biggest deal we've ever done," said Jim Lighthizer, president of the Civil War Trust, a Washington-based nonprofit group that has preserved 40,000 acres of land in 20 states. "Lee's headquarters is one of the most important unprotected historic structures in America."

Lighthizer said the trust would purchase the property, which includes a Quality Inn and a brew pub, from Belmar Partnership for $5.5 million and spend an additional $400,000 to $500,000 to demolish the modern structures and restore the historic building.

On July 1, 1863, the property was the scene of violent hand-to-hand combat between advancing Confederate troops and Union troops attempting to protect the western entrance to the town and the railroad line, which still runs behind the parcel.

By day's end, Union troops had retreated to Seminary Ridge, and Lee, the Confederate commander, established his headquarters at the house.

"It was the nerve center," historian and licensed Gettysburg battlefield guide Tim Smith said in a video produced for Tuesday's announcement at the Lee headquarters.

The house, believed to have been built in 1833, was occupied by a widow named Mary Thompson at the time of the war and was co-owned by U.S. Rep. Thaddeus Stevens - a force behind the passage of the 13th Amendment ending slavery.

The headquarters building was opened as a museum in the early 1920s in connection with the motel on the site.

Lighthizer said the artifacts, which were to be donated to the trust by the owners, would be sold and the building restored to the way it looked when Lee and his officers plotted strategy under its roof.

Lee would go on to defeat July 3 and retreat south after losing thousands of men in what is considered the turning point of the war.

"This spot is where some of most important decisions were made by an American general in the Civil War," said Lighthizer. "It had direct impact on the future of the country."

He said that there was no timetable for the restoration project or reopening the house after demolition of the modern buildings, but that the whole parcel would be donated to the National Park Service for inclusion in the Gettysburg National Military Park.

"To the preservation community, this land was long considered lost," Deputy Secretary of the Interior Mike Connor said in a statement. "Thus, the journey we embark upon today is especially meaningful: We are not just protecting a piece of American heritage, we are reclaiming it for future generations."

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