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 Montana Thrust Belt Province is located in western Montana, encompassing all or parts of Beaverhead, Broadwater, Cascade, Deer Lodge, Flathead, Gallatin, Glacier, Granite, Jefferson, Lake, Lewis and Clark, Lincoln, Madison, Meagher, Mineral, Missoula, Park, Pondera, Powell, Ravalli, Sanders, Silver Bow, and Teton counties in Montana. The main population centers (greater than 15,000 residents) within the study area are Butte, Helena, Kalispell, and Missoula. The main highways, I-90 and I-15 generally traverse the area from east to west and north to south, respectively. The province boundary was drawn to include the geologic structures generally considered to be in or bounding the Montana Thrust Belt basin, including the Thrust Belt, Helena Salient, Blacktail Salient, and Tertiary Basins.