It is called the Lodge, and for 105 years it has been the first stop for any school group, tourist, or history buff visiting the Bunker Hill Monument in Charlestown. Entering the mausoleum-like structure at the base of the famous obelisk, visitors dutifully passed a marble statue of an imposing Revolutionary War general and three dioramas from the 1970s with tiny figurines doing battle on a faux-grass hill. Created as a majestic gateway, the Lodge had become a cramped, overheated choke point, woefully inadequate for 200,000 annual visitors, officials said.

No longer. The National Park Service, after rethinking the way it presents the history of one of America's the most pivotal battles, has culled artifacts from local archives and hired a local muralist. Tomorrow, the result, an airy new Bunker Hill Museum, will open to the public. Across the street from the monument and no longer confined to the stone Lodge, the exhibits sprawl across two floors of a building that until 1970 housed the Charlestown branch of the Boston Public Library.

Inside, big colorful panels describe the battle and the building of the monument, and display cases show weaponry wielded in the bloody fight. Upstairs, in a circular painting overhead, known as a cyclorama, Arlington muralist John Coles presents images of black and Native American soldiers largely excluded from previous histories.

"The facilities were inadequate to tell the stories both of the battle and of the history of the commemorative efforts," said Martin H. Blatt, the Park Service's chief of cultural resources in Boston. "Everything was cramped into a space that was supposed to be contemplative. Now, you can come here and have a full museum experience and hear about the Battle of Bunker Hill, which really is the launching battle of the American Revolution."