The Pennsylvania Railroad (reporting mark PRR) was an American Class I railroad, founded in 1846. Commonly referred to as the “Pennsy,” the PRR was headquartered in Philadelphia, Pennsylvania.
The PRR was the largest railroad by traffic and revenue in the U.S. for the first half of the twentieth century and was at one time the largest publicly traded corporation in the world. At the end of 1925 it operated 10,515 miles of rail line; in the 1920s it carried about three times the traffic (measured by ton-miles of freight) as other railroads of comparable length, such as Union Pacific or Santa Fe. The only rival was New York Central, which carried around three-quarters of PRR’s ton-miles.