He visited the Liberty Bell.

What is this, he wondered, looking at 2,080 pounds of cracked bronze, then hanging in Independence Hall. What's so exciting?

His beaming white Masterman classmates seemed to share a good secret he did not understand. None of the rangers - all white men - who talked to the class mentioned slavery or abolitionism, the Civil War or civil rights. The African American boy from North Philadelphia left the park bemused.

He had looked at the bell, listened to talk of freedom, and thought about his own poor, hemmed-in black neighborhood. What did the bell have to do with that?

"It seemed like a big party that I wasn't invited to," recalls Coard, now a 43-year-old criminal attorney, who could not have known that more than 30 years in the future, he would be instrumental in opening the party up to everyone.

Back then, in the early 1970s, the story visitors heard at Independence National Historical Park was one of freedom, liberty and opportunity as reflected in the pale faces of Washington, Jefferson, Franklin. But today, as the city and the park service welcome tens of thousands of visitors to this week's July Fourth celebrations, the stories have changed - and changed radically.

Yes, at the bell the video and exhibits still portray liberty and freedom and Washington and Jefferson, but they also talk about slave-owning Founding Fathers, about abolitionism and the civil-rights movement. Visitors learn that the Liberty Bell was a symbol for the women's suffrage movement, for immigrants protesting discrimination in the New World, for human-rights activists everywhere. They learn that the idea of freedom evolves, that the American journey is incomplete.

None of this was part of ranger talks 35 years ago. But it's there now, largely because of a house long gone, the President's House, where George Washington and John Adams lived, worked and invented the presidency, and where Washington kept at least nine slaves.

The great change began in 2002, when scholars and citizens - including Michael Coard - were angered to learn that Independence Park officials had planned to build a new Liberty Bell pavilion virtually on top of Washington's slave quarters. The ensuing controversy compelled sweeping change in the park's narrative and allowed a host of new stories to flood onto the plain of Independence Mall.

And with the stories, told in exhibits, talks, tours and classroom programs, new characters present at the nation's creation have been brought into the light of the 21st century.

Here is Oney Judge, Martha Washington's personal attendant, who defied a president and a Constitution in her escape from slavery. Here is James Oronoko Dexter, who bought his freedom, then helped found the first free African church and self-help group in the new nation. Here is Hercules, Washington's chef, who finally had enough of bondage and disappeared from Philadelphia.

The stories keep coming: Park sites are now seen in light of their relationship to the Underground Railroad, and a walking tour exploring that theme began four years ago; lineaments of a vibrant, free African community two blocks from Independence Hall - excavated by archaeologists in 2000 before the National Constitution Center was built - are being sketched out at a new public archaeology lab; the roles of slaves and slaveholders in the early life of such beloved institutions as Christ Church are being presented to the public.

And black enslavement at the nation's birth and in its birthplace has taken its place as a painful, essential topic of discussion and commemoration. In 2010, a memorial to the President's House and its enslaved occupants is to open right outside the front door of the Liberty Bell Center.

This change is a monumental revision of America's founding mythology, historians argue - one that has not diminished the sanctity of sacred ground but magnified it.

"The whole concept of sacred ground and the creation of sacred space has been extended by what's happened," said Randall Miller, a professor of American history at St. Joseph's University, who has pressed Independence Park officials to address the issues raised by the site.

"We're not just looking for history. We're not just looking for information on free blacks or slavery. We're going deep into discovering ourselves as a nation."

In the spring and summer of 2007, Philadelphia witnessed something unprecedented, as hundreds of thousands of people streamed across the city to look at a hole - an archaeological exploration of the house site at Sixth and Market Streets.

Washington's slaves lived there when he was president and Philadelphia was the nation's temporary capital in the 1790s. Though John Adams, his successor as president and occupant, opposed slavery and held no human property, the hole kept its redolence of the unspeakable, for some a wound exposing a painful past, for others a scooped-out vessel holding a culture's complex secret self.