A detail of the photo showing Western Maryland Engine No 906 at the Thurmont Station on June 10, 1939.  There is a story about one of these beasts throwing a driver tire near High Bridge.  The engine was backed down to the siding at the station and a crew jacked up one side of the engine, heated a new tire on site and mounted it.  Due to some tight curves this was about the largest engine that could make the trip up to Blue Ridge Summit.