Since the Pennsylvania System was mentioned above, here's a Form 5 passenger timetable dated April 30, 1922 with "PS" lettering from my collection. As seen from the photo, this edition prominently featured the still relatively new Pennsylvania Station in New York City. Of course, at this time, Pennsy trains to the west were still being hauled by electric locomotives drawing their power from third rail direct current. Alternating current supplied by overhead catenary was still in the future.
Bob