It was a last-minute addition, almost an afterthought.

But against virtually all expectations, the archaeological excavation of the President's House, now more than two months running, has uncovered powerful physical evidence evoking presidents and slaves, eliciting excitement and deep interest from the thousands who have packed the public observation platform to view the site at Sixth and Market Streets.

In response, the city and Independence National Historical Park have extended the dig through July Fourth. It had been expected to wrap up about now.

"We want to take advantage of all the interest," said Joyce Wilkerson, Mayor Street's chief of staff.

"This is a national story," directly related to July Fourth, she added.

At the same time, the city and park face an extraordinary conundrum: what to do next.

Should the dig and its findings simply be filled in and the long-awaited memorial to the President's House and its residents proceed as planned? The house was where George Washington and John Adams created the presidency in the 1790s. And it was where Washington quartered at least nine slaves as he helped launch modern democracy.

Or should the findings - which include Washington's great bow window and the foundations of the kitchen and an underground passageway, the subterranean world of slaves - somehow remain accessible, open to view?

What U.S. Rep. Bob Brady saw Friday when he visited unannounced, almost anonymously, left him nearly speechless.

"I was completely shocked," he said in an interview later in the day. "I never thought anything like this would be there. I looked at it, and there was the oval window and the passageway. How can you cover that up?"