I have always found it very confusing to figure out what happened to the Pennsylvania Railroad. Where did it come from? Where did it disappear to? I have researched many books, various e-mails, web sites, and video tapes, and have come up with this simplified diagram.

The Pennsylvania RR introduced many innovations to railroading, including air conditioning, electrification, and the practice of loading truck-trailers on flat cars.

You can click on the image below to see the larger view. Some rectangles in the image on that page are clickable and will take you to the appropriate prototype or historical society web site in a separate browser window.