The U.S. State of Illinois 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.
The Office of Management and Budget (OMB) has designated more than 1,000 statistical areas for the United States and Puerto Rico. These statistical areas are important geographic delineations of population clusters used by the OMB, the United States Census Bureau, planning organizations, and federal, state, and local government entities.