Secretary of the Interior Ken Salazar, who backed Rendell and Lenfest, and Mayor Nutter, who paved the way in the city, were also on hand for the event, at the Independence Visitor Center at Sixth Street and Market.
To acquire less than an acre of the park, ARC has transferred 78 acres of open land surrounded by Valley Forge National Historical Park to the National Park Service.
The park service is also paying ARC $3.2 million and will put an additional $3 million into refurbishing buildings to make the move possible.
ARC plans to occupy part of the old visitor center for a number of years while it seeks funds to construct a $100 million museum facility - a rough estimate, since there are no architectural plans - to house its collection of Revolutionary War artifacts and documents.
"It's a win for Philadelphia and Pennsylvania," Rendell said, "and also a win for Valley Forge national park."
ARC will move operations to Philadelphia after a bruising effort to establish a big presence at Valley Forge.
For several years, ARC sought to build a museum and conference center complex on the 78 acres. Just two years ago, the cost of the ambitious project was put as high as $375 million by a former ARC official.
But conservation groups and local residents were unhappy with ARC's vision, arguing it was inappropriate for the site - too commercial and too big.
The National Parks Conservation Association brought suit, tying up the plan and delivering a crippling blow to fund-raising. ARC won the first round of litigation, but the association, an advocacy group, appealed.
That's when Lenfest and Rendell took their tour of Philadelphia, subsequently meeting with Salazar and Nutter. ARC offered to give up its Valley Forge land for the Philadelphia location.
Congress reviewed the deal and gave its blessing.
"This is a happy day," Lenfest said after hugging Rendell.
Contact culture writer Stephan Salisbury at 215-854-5594 or email@example.com