The Pennsylvania Railroad experimented with different builders and type of locomotives until they found the best design. Highlighted are various classes of steam locomotives like the K4 4-6-2, S1 6-4-4-6 Duplex and T1 4-4-4-4 Duplex, diesel's like Alco RS models, Baldwin end-cab switchers, Fairbanks-Morse Train Master, Electro-Motive GP series, F-units and E-units, along with the legendary bi-directional, center-cab GG1 electric locomotive. Also featured with this collection of previously unpublished archival photos are a system map, timetables, advertising and locomotive designs by well known industrial designer Raymond Loewy. Revised edition with 16 pages of color and revised and expanded captions.