Nonriparian woodlands occur on escarpments and other topographic breaks throughout the grassland province of central North America. Grassland vegetation is mainly correlated with gently sloping or flat terrain mantled by deep, transported soils of Pleistocene or younger age. Paleobotanical evidence suggests that extensive treeless grasslands may be a relatively recent development on the plains. Interaction of topography, wind, and fire may partly account for the observed distribution of vegetation.