SSW (Cotton Belt) SD45T-2 9404, Milwaukee Road GP40 2014, SP SW1500 2753, and SP GP9 3785 at SP Yard Ennis, Texas. An original Kodachrome slide, from my collection.
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.