It is no exaggeration to say that, in its heyday, the Pennsylvania Railroad was the greatest railroad in the world. It was certainly the largest (track-wise), hauled the most freight and passengers, had the most employees, and the largest earnings. At its peak, the PRR had 23,000+ miles of track (a figure since eclipsed by modern Class I railroads). In 1929, the PRR owned 7,000 locomotives and 282,000 cars - many built at their railroad shops in Altoona. The PRR boasted the largest railroad shops in the world (the aforementioned Altoona), and the largest railroad yard in the world (Enola). This illustrated timeline will attempt to provide a brief history of this great railroad, and also speculate on 1) why the PRR was so successful and 2) why the PRR died in such an ignominious way in the late-1960s/early-1970s. This edition has 55 photos, with 34 of them in color.