Historical review -- Stratigraphy -- Structure -- Oil- and gas-bearing rocks -- Future prospects. and Plate 1. Oil and gas fields map of the Amity quadrangle, Pennsylvania -- Plate 2. Oil and gas fields map of the Claysville quadrangle, Pennsylvania -- Plate 3. Well location map, City of Washington, Pennsylvania -- Plate 4. General information map of the Amity and Claysville quadrangles, Pennsylvania -- Plate 5. Fence diagram of the Upper Devonian and Mississippian rocks of the Amity and Claysville quadrangles, Pennsylvania -- Plate 6. A selected gamma ray and lithology log of the oil- and gas- bearing rocks of the Amity and Claysville quadrangles, Pennsylvania -- Plate 7. Stratigraphic cross section along line A-A' in Claysville, Amity, Waynesburg, Masontown, and Uniontown quadrangles, Pennsylvania -- Plate 8. Structure map on base of the Big Injun sandstone -- Plate 9. Selected wells showing positions of hydrocarbons in the Gordon zone at various locations in the studied area.