File:Pennsylvania Railroad - 5901 diesel locomotive (E7A) 2 (26958769180).jpg

This first-generation diesel locomotive is a General Motors Electro-Motive Division E7A. It was built in September 1945 and saw service as Pennsylvania Railroad # 5901 and Penn Central Railroad # 4201. It is now on display at the Railroad Museum of Pennsylvania in the town of Strasburg.

Museum info.: "Following World War II, railroads raced to replace worn-out steam locomotives and modernize passenger trains to win the traveling public back to the rails. As railroads introduced and upgraded passenger trains with new coaches, diners, and Pullmans, new power was also desired.

Introduced prior to the war, diesel-electric locomotives had been confined mostly to freight yards. The introduction of the Electro-Motive Corporation's Model FT in 1939 proved that this new motive power was also well suited for mainline service. EMD's first post-war passenger locomotive was the E-7. Its "covered wagon" design quickly became the standard face of railroading on the mainline and in popular culture and remains a perennial favorite to this day.

Generating eighteen hundred horsepower (the "E" in E-7), by using two 20 cylinder diesel engines to generate power for four electric traction motors, the E-7s were often used in pairs. The streamlined appearance and clean operation were a treasure to the railroads' marketing departments. Even more importantly, the diesel's efficiency over steam locomotives saved millions in fuel, maintenance, labor, and operating costs. 510 E-7s were built for various railroads nationwide.

Having invested millions in the development and construction of their steam locomotive fleet, and serving many major coal companies, the Pennsylvania Railroad was slow to dieselize. No. 5901 and sister 5900 were the first diesel-electric passenger locomotives to arrive on the property in 1945. They were originally intended for the South Wind, a Chicago-Miami through train over the Pennsylvania Railroad, Louisville and Nashville, and Atlantic Coast Line. At the last minute, the Pennsylvania Railroad backed out of the deal and reassigned its new diesels to the Middle Division.

The arrival of these two E-7 locomotives in Harrisburg was overshadows by the arrival of the new T1 class steam locomotives on the same day. Unsure about the new diesel-electric technology and suffering from a lack of diesel refueling stations, the Pennsylvania Railroad was reluctant to put the new E-7s to work at first. It quickly became apparent, however, that the new diesel-electrics would operate much more efficiently and reliably than the more popular T1s. In their first 6 months of service, 5900 and 5901 ran for a combined 69,000 miles without a single road failure. The most reliable T1 steam locomotive could only go as long as 2,800 miles in the same span of time. Almost immediately, orders went out to several manufacturers for new diesels to re-equip the entire "Blue Ribbon Fleet" of passenger trains. The Pennsylvania Railroad began ordering additional E7s eighteen months later, along with models from each of EMD's competitors. The E7 fleet eventually grew to 60, more than any other railroad.