High Quality Content by WIKIPEDIA articles! The South Mountain Railroad was a southcentral Pennsylvania railway line for "connecting the Pine Grove works to the Cumberland Valley R. R." and which provided mining and passenger services via a southwest section from Hunter`s Run, Pennsylvania, and a northern section from Hunter`s Run to the CVRR junction northeast of Carlisle. The northern section merged with the Gettysburg & Harrisburg Railroad line south from Hunter`s Run to the Gettysburg Battlefield in 1891 to create the Gettysburg & Harrisburg Railway line, while the branch southwest from Hunter`s Run became the Hunter`s Run and Slate Belt Railroad line.