This Excel file contains annual data for 1759-1948 and 1881-1930 by county.
The Earth and Mineral Sciences Library has a set of the Bituminous coal mine maps of Pennsylvania, created by the WPA during the 1930's. Sample images of these maps are available for Altoona and Philipsburg, and you can find the preliminary website housing the maps here. These maps are based on 15-minute topographic quadrangles, divided into nine sections. (For example, "Altoona 1" represents the northwestern corner of the Altoona 15-minute quadrangle. "Altoona 9" represents the southeastern corner of the quadrangle.)