I'm modelling kind of the WM between Baltimore and Cumberland and I want to model Hagerstown. Want was the operations for the area. I do have the Reading coming in (I know it didn't but hey its my realroad and the engines look better then PRR or PC. I was thinking of using as a coal marshalling yard.
The big marshalling yard for loaded coal on the WM was the Knobmount yard just west of Cumberland, Maryland where loads from the Gray Mine in Pa and several mines along the Elkins division in WVa were classified for eastbound drags to Port Covington at the Baltimore harbor and to Lurgan Pa for hand off to the Reading. Westbound empties were handled at the Ridgely yard located in close proximity to Knobmount.
Hagerstown was the main maintenance location for the WM. The Hagerstown yard handled transfers with the N&W, Reading, NYC, and PRR as well as east and west bound classification work. B&O transfers were worked out of Hagerstown but actually occurred at Cherry Run and Big Pond.
You are actually prototypically okay to run the Reading on your layout since the Reading had run through rights from Lurgan to Connellsville Pa where both railroads interchanged with the P&LE.
I would suggest two books if you are interested in learning more about the WM -- "The Western Maryland Railway: Fireballs and Black Diamonds" by Cook and Zimmerman, and "Western Maryland Railway 1872-1999: A Pictorial History of the Men, Women, and Machines that made it Famous" by Carroll Spitzer. The latter book focuses heavily on Hagerstown.
Poppyl