With a ribbon-cutting ceremony Wednesday near the Liberty Bell Center on Independence Mall, Philadelphia debuts an extraordinary exhibit that should surprise and challenge the many visitors who come to the city to experience the story of our nation's founding.

At the "President's House: Freedom and Slavery in Making a New Nation," visitors will see the partial walls, window frame, fireplace, and other outlines of a colonial house that stood at Sixth and Market Streets. But it's the retelling of what happened within those walls that will make for an extraordinary visit.

The former Robert Morris mansion is where the slaveholding George Washington and the antislavery John Adams lived and conducted their presidencies in the 1790s. Washington quartered nine enslaved Africans who served his household - a small contingent from among 300 slaves owned by the man revered as the father of his country.

So, the story told by the President's House exhibit will be unlike any operated by the National Park Service - a narrative that delves into the bitter irony of slaveholding Founding Fathers, who crafted a Constitution that denied the promise of freedom to blacks. But it's also a story of hope. Martha Washington's personal servant, Oney Judge, escaped to freedom from this same mansion.

How fitting, then, that the first federal commemoration of slavery be set in Philadelphia, where the nation's fundamental freedoms were enshrined. Moreover, the President's House project offers a dramatic contemporary story line that hints at racial divisions yet to be healed.

The exhibit's original plans didn't include as much of an emphasis on slavery. It became a memorial to Washington's slaves only at the insistence of groups such as the Avenging the Ancestors Coalition, led by local attorney Michael Coard, which deserve much of the credit for prompting a redesign of the President's House to assure that the slaves' story is told.

Playing an equally pivotal role, then-Mayor John F. Street prompted the first major public exposure of the interplay of slavery and the nation's founding with his order for a 2007 archaeological excavation, a dig that was viewed by an estimated 300,000 people.

It's inevitable there will be disputes as to whether the exhibit achieves the right balance. But there can be no doubt that the President's House opens a unique window on the quest for freedom.