I am trying to research specifically the area just west (perhaps slightly north) of philadelphia. I drive by Roosevelt blvd daily, and I notice how beautiful the rolling hills of the Olney, Logan, and Germantown sections of philadelphia are. There are tracks that run from west philadelphia, over the schukyill (next to girard) all the way through fairmount park, strawberry mansion, etc. then into the upper north western areas of the city, beyond into montogomery county, I suppose eventually heading into valley forge.
My questions are generally as follows:
1)Which steam engines used to run these tracks back then?
2)What major stations did they use at the time along this route?
3)Steamers at ZOO interlocking? Or only the electrics like the GG-1?

Specifically did these engines ever go east of Harrisburg even lets say at least 75 miles west of philadelphia, not into the city of course, but perhaps relatively near it?
And how far east did the J1 2-10-4’s run?
You see, lately, I have been driving by these tracks in philly and following them, trying to imagine what sort of steam or diesel ever went just west beyond these areas of the city into montogomery county?
Unfortunately, I can’t travel anytime soon to beyond harrisburg where supposedly the big steamers that mentioned apparently reigned. My schedule is too hectic.
Also, can someone give me a general quick history on PRR electrification, causes for it, how it affected diesel and steam operations. I have tried to look into this, but I would like to hear a real history buff set me straight on this issue.
Many questions