Also known as: PRR, Pennsy
A massive Class 1 railroad in the Northeastern United States which operated from 1848 to 1968 when it was merged with it's rival the New York Central to form the ill fated Penn Central. Billed as the Standard Railroad of the World the PRR was a industry powerhouse in the northeast till it finally started loosing money for the first time in it's history in 1946. In the end this titan of a railroad was brought down by the pride and arrogance of it's management and corporate officers.
Better reading than my typing
https://www.american-rails.com/pennsylvania-railroad.html
https://en.wikipedia.org/wiki/Pennsylvania_Railroad