There is no doubt that Philadelphia tells a compelling story about the birth of a new nation, and this museum delves into it. Inside a $125 million Robert A.M. Stern-designed building, a comprehensive experience “follows the journey of America’s founders,” says R. Scott Stephenson, the museum’s top curator. “But it also recovers the populism of the movement and attempts to broaden the idea of who exactly that founding generation was.” The crux of the whole experience is the 16,000-square-foot core exhibit, which expands greatly on a small collection that had been located at Valley Forge for decades. Joint tickets available. $13-$21, children under 6 free. Open daily; extended hours in summer.