People today tend to overlook the fact that, until Penn Station and the North River Tunnels were built, Philadelphia, rather than New York, was thought of as the Pennsy's "natural hub", and the perception did not change overnight. A number of sources show intermediate-distance passenger runs to places like Pittsburgh and Cleveland originating at Broad Street Station well into the 1920's.
I suspect that this was due in part to the development of more service to the south via Washington as Florida boomed in the Twenties; capacity to accommodate additional service from the west on the Main Line north of Philly was not all that great. And service to Buffalo always originated primarily at Washington, and was easily coordinated with the large volume of east-west service at Harrisburg. There were also two daily trains to Wilkes-Barre via the Schuylkill Branch, the last of which came off in 1941, and going waaay back, to Scranton via the Bel-Del and the DL&W.
What I would like to uncover is a plan of the Philadelphia Terminal area before the installation of the "mega-towers" at ZOO and ARSENAL. That must have been a very complicated arrangement.
What a revoltin' development this is! (William Bendix)