The Pennsylvania Railroad's class P5 comprised 92 mixed-traffic electric locomotives constructed 1931–1935 by the PRR, Westinghouse and General Electric. Although the original intention was that they work mainly passenger trains, the success of the GG1 locomotives meant that the P5 class were mostly used on freight. A single survivor, prototype #4700, is at the National Museum of Transportation in St Louis, Missouri.

The Pennsylvania Railroad, legal name The Pennsylvania Railroad Company, also known as the "Pennsy", was an American Class I railroad that was established in 1846 and headquartered in Philadelphia. It was named for the commonwealth in which it was established. At its peak in 1882, the Pennsylvania Railroad was the largest railroad, the largest transportation enterprise, and the largest corporation in the world.