In 1994 the Utah Geological Survey (UGS) Mapping Program began an extensive geologic mapping effort in the greater St. George area of southwest Utah. Currently, we have completed nine 1:24,000-scale quadrangles that were funded with a 50:50 cost share under the National Cooperative Geologic Mapping Program (STATEMAP component), and a tenth quadrangle is in progress. Along with eight newly mapped quadrangles of the adjacent Zion National Park area, which were jointly funded by the National Park Service and UGS, these maps provide unprecedented geologic map coverage of over 2,700 km2 across the western margin of the Colorado Plateau and adjacent transition zone with the Basin and Range Province. Already, the maps have: (1) formed the basis for a GIS-based geologic hazards map folio of the burgeoning St. George basin; (2) served as a guide to paleoseismic investigations of the Hurricane fault; (3) formed the foundation for general-interest geologic reports on Zion National Park, and Quail Creek and Snow Canyon State Parks; (4) provided new insights into Quaternary landscape evolution based on new long-term incision rates along the Virgin River; and (5) improved our understanding of ground-water resources. The maps have also been a major resource in ongoing efforts to set aside habitat for the endangered desert tortoise, and to delineate scarce sand and gravel resources before they are covered by construction.