Over the door of this old substation control building is “19 A.E.P.Co. 31”. I think this refers to “Appalachian Power Company”. I can’t be sure, because Appalachian Power Company was bought by American Gas and Electric Power Company (now AEP) in the late 20s.
This just off 460 on Red Ash Road northwest of Richlands VA at 37.11652, -82.87015. Red Ash was a large coal operation back in the day. Note the old power line support tower on the right.