The U.S. currently has 47 statistical areas that have been delineated by the Office of Management and Budget (OMB). On July 21, 2023, the OMB delineated 14 combined statistical areas, 12 metropolitan statistical areas, and 21 micropolitan statistical areas in Illinois. As of 2023, the largest of these is the Chicago-Naperville, IL-IN-WI CSA, comprising the area around Illinois' largest city, Chicago.