You might be surprised

It depends on where the RR is getting their coal, and where the rest is coming from.  Chances are pretty good that it is going to be as local as possible, meaning somewhere in New England or the upper Atlantic Seaboard (i.e. Pennsylvania RR, NYC, maybe B&O or C&O).  However, if your railroad or the shipyards need a specific type of coal which was only available in a specific part of the country, or if they have a very close relationship with some other railroad, that could influence the source and therefore the cars the coal is coming in.

However, in general I would suggest sticking with a couple close roads, or home road cars.  It will help make things seem right (a Union Pacific car in Maine might stand out a bit), and it makes the most sense.

What were the other roads doing?

You might look through some books on the MEC, B&M, NH, BAR, etc, and see if they have any photos showing hopper cars. Being strictly New England roads, they would have the same problem of having to get coal from somewhere off line. Also consider that there used to be a lot of ocean going barge movement so it is conceivable that if your railroad serves a port, they could get their coal by barge and move in their own cars. Also there were coal mines in Nova Scotia although that would add customs fee to the cost of the coal.

Posting on Black Friday...

I forgot about barges and coal ships--and me a New Englander!  I guess one should never post after working retail from 7:30 PM on Thanksgiving until 6 PM the next day, with only a 4 hour sleep in the middle!

Coal

I've seen photos of CP Rail

I've seen photos of CP Rail hoppers for hauling coal on the BAR and MEC.    The BAR also hauled coal out of Sears Port for the mills and air force base right into 90's, when the last of the mills converted to oil or gas.   MEC had coal docks in  Portland and also took some coal out of Bath.

Operations like the 2 foot gauge Kennebec Central Railroad was set up to haul coal from Randolph to Togus about 8 miles.  The railroad had no out side connections and was set up to haul coal and passengers to the Veterans Home from the Kennebec River delivered by schooners and barges.

Hope this helps.

John

B&M

The B&M had to deal with delivering anthracite and bituminous coal.  From what I've been able to determine, the anthracite (hard coal) was brought up from the hard fields in NE PA in anthracite road cars (Reading, Erie, PRR,etc.) cars. These loads would serve local coal dealers to serve the home and small business fuel market.  Bituminous coal would be shipped from the Tidewater region via collier or barge, offloaded, and delivered on home road hoppers.  This coal would service industrial users and the railroad itself.

Portsmouth NH had large coal bunkers where coal was offloaded from ships and barges and loaded onto B&M hoppers.  The Sanborn maps from the earlier part of the 20th century show a number of these bankers and the related trackage.  That entire area was virtually leveled in the early '90's in an urban renewal effort.  If I could find enough photographic documentation I'd be tempted to model this area as it once was on a shelf layout. 

Jerry