Erosion surfaces on the Piedmont and the Appalachian Plateaus are described. Ridges and valleys in the Valley and Ridge Province are probably not erosion surfaces, forming instead due to lithology differences in the underlying rocks. The "cycle of erosion" invented by William Morris Davis was once popular but has many problems. The currently popular weathering hypothesis is also analyzed and found wanting. The formation of the erosion surfaces with monadnocks and veneers of gravels transported over long distances is best explained by mechanisms associated with the retreating stage of the Flood.