The USGS Central Region Energy Team assesses oil and gas resources of the United States. The onshore and State water areas of the United States comprise 71 provinces. Within these provinces, Total Petroleum Systems are defined and Assessment Units are defined and assessed. Each of these provinces is defined geologically, and most province boundaries are defined by major geologic changes. The Southwestern Wyoming Province is located in northeastern Utah, northwestern Colorado and southwestern Wyoming, encompassing all or parts of Eagle, Garfield, Moffat, Rio Blanco, and Routt Counties in Colorado and all or parts of Carbon, Fremont, Lincoln, Sweetwater, Sublette, Teton, and Uintah Counties in Wyoming and all or parts of Summit and Daggett Counties in Utah. The main population centers within the study area are Casper, Evanston, Green River and Rock Springs Wyoming. The main highway, I-80, generally traverses the area from east to west. The Green River, Yampa River and their tributaries drain the area. The province boundary was drawn to include the geologic structures generally considered to be in or bounding the Sand Wash Basin, Washakie Basin, Great Divide Basin, Hoback Basin and Green River Basin.