ZCTAs are geographic areas created by the US Census Bureau to approximate the delivery areas of ZIP Codes for statistical analysis. While ZCTAs use the same five-digit codes as ZIP Codes, they represent defined geographic areas that may not exactly match the mail delivery routes of ZIP Codes.
ZIP Codes and ZCTAs (ZIP Code Tabulation Areas) serve different purposes. ZIP Codes are postal codes created by the USPS for mail delivery, and are not correlated to geographical coordinates. ZCTAs provide a way to analyze census data in relation to ZIP Code areas while maintaining geographic consistency and protecting privacy. In addition, there are more ZIP Codes than ZCTAs, because many ZIP Codes for PO Boxes or unique entities don't have corresponding ZCTAs (US Census).
The data shown reflect ZCTAs from the US Census. As of 2024, there are 1,387 ZCTAs in Illinois (US Census).