The recently renovated and reopened Philadelphia History Museum showcases an impressive collection of art, objects, and artifacts spanning 330 years of the city's history. Dating back to 1826, the building itself plays into the journey through the past.
The biggest draw for me, however, is the rotating Made in Philadelphia exhibit which looks at the city's contributions in craftsmanship and manufacturing throughout history (particular nod to the 'Craft Brewing' feature which focuses on brewing from the days of William Pen right up through the revival of microbreweries in the 20th century).
And if you're keen on vintage Philly, I highly recommend the much-lauded Facebook page Old Images of Philadelphia. It isn't associated with the museum but offers a heartwarming virtual walk through the city's storied past.