The incident occurred on Monday between 7:30 p.m. and 8:00 p.m. at Gaul and Letterly streets.
Police say a 14-year-old girl was approached by two unknown males who forced her into a vehicle.
They drove her to Richmond Street and Lehigh Avenue where one of the males forced her out of the vehicle, then to nearby train tracks, where he sexually assaulted her.
Police have released a sketch of this suspect. He is described as a black male between 19 and 21 years old. He is said to be 5'9 with a brown complexion, a thin build, and a beard and mustache.
There is no description of the second male.
The vehicle is described as a black, square-designed automobile with red doors.
Anyone with information is asked to contact Special Victims Unit at 215-685-3251 or 3252.