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 Raton Basin-Sierra Grande Uplift Province is located in South Eastern Colorado and North Eastern New Mexico, encompassing all or parts of Custer, Huerfano, and Las Animas counties in Colorado and all or parts of Colfax, Harding, Mora, and Union counties in New Mexico. The main population centers within the study area are Trinidad, and Walsenburg Colo.; and Raton, New Mexico. The province boundary was drawn based on county lines to include the geologic structures generally considered to be in or bounding the Raton Basin-Sierra Grande Uplift Province