Location of land areas and depositional basins are interpreted from distribution of lithofacies and thickness of Pennsylvanian and Lower Permian rocks. Principal Early Pennsylvanian positive elements were the Ancestral Front Range, Black Hills and Chadron arch, Transcontinental arch, Rosebud arch, Bannock highland, and Pathfinder uplift. The sea transgressed between these positive elements onto the Wyoming shelf from both southeast and southwest. Terrigenous sediments, derived chiefly from the Ancestral Front Range, tongue basinward into carbonate and evaporite rock and are thickest in the Powder River basin and Lusk embayment. An additional area of uplift is recorded in central Wyoming in Middle Pennsylvanian and Early Permian but otherwise the depositional patterns were similar until Middle Permian when deposition became dominated by a transgression from the west.