Iowa Census ZIP Code Tabulation Areas

Description taken from the US Census ZCTA Website. First introduced in 1963, ZIP Code is a trademark of the USPS created to coordinate mail handling and delivery. The USPS assigns ZIP Code ranges to regional post offices, which in turn assign ZIP Codes to delivery routes. Each delivery route is composed of street networks, and/or individual units with high mail volumes, such as high-rise buildings or individual business locations. Within the Census Bureau’s MAF/TIGER System, ZIP Codes are stored as one component of discrete addresses tied to delivery points, including specific housing unit locations. The result is a point-based dataset unsuitable for mapping and many analysis applications. ZCTAs are generalized areal representations of the geographic extent and distribution of the point-based ZIP Codes built using 2020 Census tabulation blocks. The Census Bureau is restricted by Title 13 from releasing individual housing unit addresses or location information to the public, so point-based ZIP Code data are unsuitable for distribution and publication. However, by aggregating the points and extrapolating them to a polygonal-based unit (census tabulation blocks), disclosure concerns can be addressed and “geographic subtraction*” is prevented.