Geological Map of Western Allegany County

This map from the 1968 Maryland Geological Survey shows the location of coal in the George's Creek valley, from Frostburg to Westernport, with Lonaconing roughly halfway between the two towns. The purple color labeled PM is the Monongahela Formation, containing coal. The Maryland Geological Survey webpage has additional information:
http://www.mgs.md.gov/esic/geo/allw.html