This line was part of the Pennsylvania/Penn Central line from Harrisburg to Hagerstown, MD. Between Harrisburg and Shippensburg it was paralleled by a Reading line several miles further south. Both companies became part of Conrail in April 1976, and this line was probably abandoned around that time.
The line passed through wooded and agricultural areas. The western section is bein developed as a rail trail, while the eastern section is used as a utility corridor. The utility corridor section can be easily located by the power lines, but the property owners have posted "No Trespassing" signs in several locations.
A short segment, from Isle to Carlisle, appears to still be active with a shipper that uses tank cars.
This view shows the Pennsylvania/Penn Central RR right of way facing east near Pa. Rte 465, between Greason and Isle. There might have been a bridge over the highway [behind the camera] at this location, judging by the grades, but all traces of any bridge have been removed. Photo from November 2003 courtesy of Mike Palmer.