This map has been prepared primarily by photointerpretation, using mainly 1:120)OOO-scale true-color aerial photographs, supplemented in places by 1:120,000 and 1:60,OOO-scale color-infrared aerial photographs. The published Soil Survey Reports on the Tucson and Casa Grande areas provided useful ground control, but their coverage is limited essentially to farming areas in the Santa Cruz River valley. Field-check traverses were made throughout the area, the density of traverses depending upon the variability and complexity of geomorphic and soil relationships and upon the available roads; additional field checks will be made before the final map is prepared. Soil associations, western half of the Tucson 1o x 20 Quadrangle; (a) northern half, (b) southern half. Scale 1:120,000