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 Michigan Basin Province is located in all of Michigan, except for a small portion of the Upper Penninsula, eastern Wisconsin, northeastern Illinois, northern Indiana, and northwestern Ohio. The main population centers within the study area are Detroit, Grand Rapids, Lansing and Flint, Michigan; Milwakee, Wisconsin; Chicago, Illinois; Fort Wayne, Indiana; and Toledo, Ohio. Numerous Interstate highways traverse the province from north to south and east to west. The province boundary was drawn to include the geologic structures generally considered to be in or bounding the Michigan Basin.