I don't live in Pennsylvania,

I don't live in Pennsylvania, but I did visit the Strasburg Railroad.  Freight and passenger, steam and diesel.  It could be interesting...very scenic.

Conrail...

...C&F Secondary. Small yard, 2 branches off the main, 3 trains, a lot of big and small customers. Non signaled, NORAC Form D, yard limits rules. 

So Many Choices

Lars, 

As a PA native you have picked a state packed with railroads and inspiration. 

To help us can you narrow it down to a time period? The area you have mentioned offers a ton of potential.

Pennsylvania

Reading and Northern

     It really has everything even passenger and steam operations. Lots of you tube videos for research.

It also has anthracite coal operations.

NS Cove Secondary

The line branches off the main in Altoona & runs to Hollidaysburg where it interchanges with the Everett railroad. Along the way it switches several industries including the Curry Rail facility in Hollidaysburg. There is a signal in Altoona that guards the Cove Secondary and I believe it is the only one on the line. Power is usually GP38-2s or GP40-2s and once in a great while you see six axle units show up to haul a long string of cars that were stored in the Curry yard. 

Looking at online photos from back in the PRR days the line was much busier along with offering more switching opportunities and it was signaled. There was a variety of motive power both steam and diesel with much longer trains than today. There was even a tower at the wye in Duncansville and further down the line in Hollidaysburg a decent size station for passenger service. If you wanted to model just a portion of the very large Sam Rea shops (now Curry Rail)  it could keep an operator busy for quite sometime.

I am not sure if this is what you are interested in or not.

PA Lines

PRR Schuylkill Secondary, Phillie to Shamokin

RDG W&N Branch, Reading to Wilmington, DE

LNE

MPA

If you are "narrow minded", the EBT is neat railroad.

A lot of it depends on era.  Once you get past the 1930's a lot of the single track lines lose their passenger service.  Once you get past the 1950's the coal business in the eastern part of the state drops off.  Short line spin offs start up in the late 1970's, 1980's.

The more mountainous, the more rural, the less on line industry.  Close to the SE (Phillie)  or Pittsburgh area, the denser the industry.

Shortlines

There are a lot of interesting shortlines in PA if you’re interested in present day railroading.  The Gettysburg RR, East Penn, Wellsboro & Corning, etc.  Not multiple trains a day, but plenty of interesting operation and in many cases nice scenery.

Any interchange!

I lived a short time in the NY Southern tier.. Erie country.  It's intersection with NYC inspired my freelanced layout.

You have Starucca Viaduct, the Lackawanna viaduct/ upper Susquehanna valley / Scranton region.

Almost any Pittsburgh servicing RR, through the Ohio R Valley... all those bridges to pick from...

Abandoned routes All Over the Place!  (Erie to Pittsburgh - high trestle destroyed by tornado in Bradford region)

The NEC in Philadelphia... intersections with Reading and PRSL to NJ. (Way too dense to do accurately)

Mauch Chunk (Jim Thorpe) and inclined planes operated by NJ.

And OMG, the Lehigh Valley... beauty and density.

You're cursed... with too much to pick from!   good luck!

Endless Possibilities

Plenty of good suggestions. Here's a link to a map. Yes, the on-line map is impossible to read; but, if you save it, then you can open it and zoom in to read.

https://www.dot.state.pa.us/public/Bureaus/railfreight/parail.pdf

Lots of possibilities, I'm going to recommend some short lines that interchange with a Class 1: 

LVRR - Lycoming Valley Railroad

RBMN - Reading Blue Mt. & Northern Railroad

SVRR - Shamokin Valley Railroad Corp

Terry

...C&F Secondary. Small yard,

Where was the C&F located?

The Pittsburg & Shawmut Railroad, also known as the Shawmut Line

This is my "bucket list" model railroad. 88 miles of track in Western PA that could easily be scaled down and accurately represented in a large room or basement. For those that love coal it is a great option.

Incorporated in 1908 the PS&N stretched from Brockway to Wayland, New York with branches to Hornell and Orlean, New York, and Tyler, Pennsylvania.)

The P&S was then extended to Freeport where it connected with the PRR. The new line, following the Allegheny River for part of its length, also connected with the Baltimore & Ohio Railroad in West Mosgrove and included four tunnels and two viaducts:

• Mauk Tunnel (1,989 feet)
• Sprankle Viaduct (1,430 feet long, 150 feet high)
• Coutler Tunnel (2,035 feet)
• East Branch Viaduct (1,478 feet, 128 feet high)
• Knoxdale Tunnel (812 feet)
• Mahoning Tunnel (1,040 feet)

By the early 1930s, the P&S was offering basic passenger service via a gasoline-powered “Doodlebug” to haul children from school in Kittanning and Brookville, and passenger operations were discontinued in 1938.

Cove Secondary - Very close to what I’m doing

Very familiar with the Cove Secondary.  In fact, I’ve designed a small layout influenced by the Everett railroad around Martinsburg.  If I had a bit more space to do things justice I would model it almost to a T.  It lends itself to model quite well.

To help us can you narrow it

Honestly, I can’t find too many things that inspire a main line model railroad.  A lot of the lines in PA are too big and too complex to model, lack on-line industry, don’t have much variability in traffic but still run enough to trains a day to make an interesting operating session.

I’m just finding that a line that you particularity love or railfan often isn’t necessarily a good line to model (B&O over Sand Patch is up there for me).  When you look at some of the really nice layouts, there is a bit of a Goldilocks scenario that when finding prototypes you need to find something that’s just right.

This is purely academic, so whatever floats your boat.  Personally, I would like to learn a bit more from 1970 to present, although before that I’m sure brings in some interesting subjects. 

Also a P&S fan

I’m starting to learn a little more about the P&S.  Love the red, white and blue switchers.  It kind of reminds me of a western PA Lehigh Valley.

As much as I like reading about it, I don’t think I would model it for the same reason I wouldn’t model the PRR/CR/NS Mon Line or some Anthracite lines - you have to really love hoppers and coal, and lots of coal traffic isn’t my cup of tea.

lars_PA

We live only a couple of miles from the Everett Railroad headquarters. I love the shortline railroads & Everett is still pretty active. Duncansville to Martinsburg would be very cool to model. The paper mill itself in Roaring Springs would provide a lot of different rail cars and operation possibilities. Years ago Conrail shared the line with Everett to the mill, I can't remember if Conrail switched the mill but I know they would get ballast from New Enterprise which was right by the mill. I will be looking forward to see what you decide to do.

Great balance on Everett

Yea, the Everett lends itself to modeling well.  The western leg has moderate sized warehouses that take a mix of traffic and switch well.  The area around Martinsburg could up to 4 feed mills, depending on modeling year, which gives you a Midwestern feel in Central PA.  The paper mill is the biggest industry by size, but could still be compressed,  Traffic includes rock, grain, lumber, chemicals, LPG, and lots of boxcar traffic.

Montour

If you like the P&S give a look at the Montour.

Too many roads to choose,

Erie Lackawanna from Binghamton to Scranton, the Lehigh Valley, the Reading, the D&H, PRR all over, the B&O that ran up to Buffalo and Rochester, go back to steam era, theO&W and L&NE. Check them all out.

would make a good model RR?

I'd probably go with the Ma and Pa. It was small enough to be able to model very realistically and simple enough to not need a huge outlay for track and rolling stock. It is also well documented so research time and effort would be mimimized. I like the photos of the Ma and Pa diesel era with EMD switchers which are readily available in S scale so that's a big factor in my choice.....DaveB

C&F

Came off the Reading at Alburtis. At one time it ran all the way to Catasauqua where it connected to the LV and L&NE. Cut back now to Fogelsville. As busy today as when it was a Reading branch line.  Different traffic but still busy. Another line to look at is the PRR Buffalo line. Runs from Harrisburg to Buffalo. Numerous branches came off along the way.  --  Ken 

I will have to look up the

I will have to look up the C&F.  I was definitely thinking about the Buffalo line.  I’m familiar with it around Williamsport, Lock Haven and Renovo,  but not much between Williamsport and Harrisburg.  I was thinking of the PRR lines between Williamsport and the Southern Tier as well, but they seemed to be heavily in decline by the time Conrail came around.

Ken McCorry did the Buffalo line on steroids, adding the steel mill and a few other things. However, I think it could be done in something not as big as a barn.

Buffalo Line

I’m originally from Millersburg, other than the line that branched off and headed east/northeast to the Williamstown colliery, there isn’t much between Harrisburg and Sunbury. During the PRR days, this line was very active in bringing coal from the anthracite mines, where it was also loaded onto barges in the canals. After Penn Central, this line was the Lykens Valley Railroad, eventually abandoned and torn out by Conrail

Lots and lots of potential.

excellent possibilities abound in a state like PA. I’d look at the Pennsy’s Northrrn Central lines for one example. The stretch of line from Sunbury to Williamsport offers moderately busy traffic including passenger traffic and considerable industry. Same with the section of line from Harrisburg to York, PA.  Emporium to Erie is an interesting line as well with online industry and several trains a day in Pennsy times.

The Lehigh Valley area from Lehighton to Easton, PA offers lots of industry and numerous railroads. Maybe the Lehigh Valley line from Lehighton to Hazelton could be considered. For something different, Reading’s Newtown Branch has high appeal. I’ve been attracted to this line ever since MR did a “railroad you can model” type article in the early 60’s. It was a commuter terminal with an unusual trackage arrangement, fully illustrated. Bethlehem Car Works makes the exact passenger cars you’d need and the road switchers used on the line are readily available. I might still end up modeling this interesting operation. There was quite a bit of industry along this line as well, giving a daily way freight plenty of business.

Barry P

Here’s a book I snatched up off of EBay

a few weeks ago. I don’t model PA but being somewhat of a shortline junkie I couldn’t pass up this book full of color photos.
 

The Wellsville Addison and Galeton:

The Maryland and Pennsylvania: