Work to tear down the Cyclorama Building began a month ago with asbestos removal and is expected to last until late April, park spokeswoman Katie Lawhon said Monday.
The removal is part of the National Park Service's longstanding efforts to restore the park to conditions more closely mimicking 1863, when the property was engulfed by a pivotal battle in the American Civil War.
"Anyone who studies the Battle of Gettysburg learns about the Union fishhook, and it's the shape that the battle lines of the Union Army took," Lawhon said. "This building was right in the middle of the fishhook, and it blocked people's ability to kind of connect the dots."
The nearly $600,000 cost of the repairs is being paid by the Gettysburg Foundation.
The Cyclorama Building opened in 1962 as the park's headquarters and visitor's center, though the visitor's center later moved to another building—which has also been torn down.
The building, designed by architect Richard Neutra, housed a 377-foot circular painting of Pickett's Charge by Paul Philippoteaux. The painting was restored and moved to a new visitor's center in 2008.
A legal battle over the fate of the building led to a court-ordered analysis of the structure and alternatives to demolition. In January, the Park Service announced the results of that study had cleared the way for a decision to tear it down.
A 1999 Park Service report called for restoring more of the battlefield to 19th-century appearances. That has included removal of structures such as a large observation tower and work on fields and fences.
Eventually, the park plans to remove a parking lot from the area by the visitor's center that was torn down in 2009 and reduce the size of the lot by the Cyclorama Building.
The battle pitted Northern troops on their own soil against the Confederates under Gen. Robert E. Lee. Afterward, Lee's troops returned to Virginia, although the war continued for two more years.
The 150th anniversary of the battle will be commemorated in July, and ceremonies are planned for November to mark President Abraham Lincoln's famed "Gettysburg Address."