Old SEPTA Brochures for the Bethlehem Branch can be found here:
http://oldtrainschedules.com/?cat=8
A Recap:
There was 9 Trains a day each way. Going all the way to Allentown to the old Reading Terminal.
The stops in the Lehigh Valley were:
Allentown
Bethlehem
Hellertown
Center Valley
Quakertown
