It happened in the 2000 block of South Broad Street late Thursday afternoon.
Witnesses say one car stopped. The other kept going.
"I was just appalled," said Brett McGinley, who witnessed the accident. "I was just shocked. I didn't know what to think. It was just so . . . Oh, my God!"
The sidewalks were crowded when the hit-and-run happened around 4:30pm.
Philadelphia Police say the girl stepped out from between two cars which were parked in the median.
She was standing in the northbound lane when an older model, silver Pontiac Caravan struck her.
"I don't know if the guy saw her, if the guy didn't see her or what," said McGinley. "He just didn't even slow down."
The impact tore off the passenger side mirror of the vehicle, which turned right onto Mifflin Street.
The injured girl was rushed to nearby Jefferson University Hospital where her doctor told me she suffered two broken legs and injuries to her head and pelvis.
The good news for her is that she'll survive.
The bad news for the hit-and-run suspect is that a surveillance camera from a nearby Dunkin Donuts captured video of the incident and police have a copy.
"Number one, they created a lot of problems for themselves because it was an accident," said McGinley.