File:PittsburghCoalExtent.png

English: Original Caption: "Map of the Horizon of the Pittsburgh Coal Bed in Pennsylvania, West Virginia and Ohio -- The Maryland deposit is excluded. It will be noted in the illustration that in West Virginia there is a line which shows where the Pittsburgh bed becomes thin and of little commercial value. While some of the deposits west of that line in Ohio are of considerable value, many are utterly valueless, and some are mere traces. In other places, the bed is missing and its horizon alone can be determined. As this is a map covering the horizon of the coal bed and not its actual presence, the profitable coal area, especially in Ohio and West Virginia, will be considerably smaller than that shown."