Those who preserved history played a key role.

On Feb. 27, a news conference was held at Independence Visitors Center to announce that Kelly/Maiello Architects & Planners of Philadelphia would create and build the long-awaited commemorative installation at the site of President's House on Independence Mall.

The product of five years of controversy, the installation will mark the site of the house at Sixth and Market Streets, where both George Washington and John Adams lived while president in the 1790s, and where Washington kept at least nine people in slavery. Much of the controversy focused on whether that fact would be acknowledged - and indeed, this would be the first national memorial to do so.

It was a great day for history in Philadelphia. Presenters at the event effusively thanked the many who worked through their differences to make this happen. But for all the gracious thanks and applause, one of the most important ingredients in the success of this effort was silently excluded - namely, centuries of preservation and stewardship of the crucial historical records by scholars, collectors and archivists. Without those knowledge workers, the stories of President's House could not have been recovered at all, let alone used to build a better future.

I raise this point not to diminish by one iota the signal importance of both citizen activism and political leadership in making this installation happen. Citizens and leaders turned what was potential into something actual. But the knowledge workers are the ones who took care of the potential through all the years when others did not know or did not care about this story. Knowledge workers may not serve the tourists, at least not directly, but the President's House project proves without a doubt that they serve this city.

At the announcement, Rep. Chaka Fattah (D., Pa.) rejoiced that, after the lapse of centuries, America was now ready to tell some truth.

"You can't have reconciliation without truth," he said. And with truth and reconciliation, he affirmed, the city and nation could move forward toward justice.

In the case of President's House, perhaps more vividly than in many other situations, the truth that pointed us toward these lofty hopes lay in historical documents, itemized in prosaic letters, deeds and account books. Through the centuries, though the story was neglected, the documents were preserved - many at our own Historical Society of Pennsylvania - in trust that some future Americans would have the ears to hear and the eyes to see. That we, now, are those Americans should indeed make us proud and happy.

But we owe our opportunity today to the historical societies, Pennsylvania's and others, that provided the shelter these documents needed to survive generations of Americans who could not or would not see, whose resolve faltered before the legacy of slavery amid freedom.

Today, historical societies continue to work in the same spirit of trust, in the hope that people in centuries to come will bring their own concerns, courage and clarity to understanding the past. Because today's societies remain committed to the immense and expensive work of storing and sheltering historical documents, our descendants will be able to follow in our steps, coming to know us perhaps better than we know ourselves.

For now, if Philadelphia grows and thrives by finally telling the liberating truth of the slaves at President's House, let us include in our celebrations a tribute to, and real support for, the dedicated caretakers of the historical record. They are the underground waters without which our wells of knowledge would run dry and our thirst for understanding go unquenched.