The Reading and Chessie System had run-through services to Allentown, Pennsylvania in pre-Conrail days. Here a Chesapeake & Ohio SD40 waits for its return assignment at Bethlehem Engine Terminal.
The EMD SD (special duty) series are a strong and reliable kind of locomotive which still serve America's rails today. They have proved themselves reliable by clocking in several million miles of freight service over several decades.