I believe this is White Mullberry (Morus alba), hanging over a sidewalk in North Philly. I first noticed similar, serrated leaves in an empty lot in South Philly a few years back, and only just yesterday made the connection that these have fruit this time of year, and were likely Mullberries.

Assuming they are indeed White Mullberries, they were originally brought over from Asia to feed silkworms, have since escaped, and are now enjoying colonization of urban spaces in Philadelphia and elsewhere.