Counties are the primary legal divisions in Illinois.
Source of definition: U.S. Census Bureau, Geography Division. Geographic Terms and Concepts – County or Statistically Equivalent Entity
Date of definition: July 2012
Note on number of counties and yearly changes in counties: There are 102 counties in Illinois. The number of counties has remained stable since the middle of the 19th century.
Note on data availability by county: The county is the principal geographic region for presentation of data on IECAM. All site-based data (e.g., child care), most non-site-based data (e.g., early intervention), and almost all demographic data (e.g., population) are presented by county.
Web Resources: Geographic Regions
- IPUMS-USA’s “Composition of PUMAs and Super-PUMAs”
2000 PUMAs and on the composition of the 2000 PUMAs by state
- United States Census Bureau: Geographic Terms and Concepts –
- Illinois Department of Human Services: Division of Human Capital Development (HCD)
- United States Census Bureau: 2010 Census Public Use Microdata Area (PUMA) Reference Maps – Illinois
A list of which counties and/or which parts of counties are associated with which PUMAs, and for maps of the 2010 PUMAs for Illinois