ABSTRACT Students of the American frontier have assumed that the myth of the Great American Desert was derived from the notions of a few men rather than from the probable reality of the experienced environmental conditions. The “illusion’ of the Great American Desert has not been considered from a climatological perspective; no serious attempts have been made using historical methods and techniques to establish the actual climate of the region during the period of formation of the desert image. Explanations concerned with the derivation of the notion of a trans-Missouri desert as perceived by early American explorers neglect the possibility of climatic variability sufficient enough to justify the disparaging accounts of the territory. By establishing the statistical relationship between tree growth and climatic characteristics, spatial reconstructions of moisture conditions in the western United States permit analysis of exploratory experience in perspective with climatic stress. One must conclude that St...