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Zip Code Tabulation Areas (ZCTAs)
Zip Code Tabulation Areas (ZCTAs) are entities created by the U.S. Census Bureau for initial use in tabulating summary statistics from Census 2000. ZCTAs are not U.S. Postal Service ZIP Codes. ZCTAs are a generalized grouping of census blocks whose addresses mostly have the same U.S Postal Service ZIP Code.
Zip Code Tabulation Areas cover all land and water areas within a state and must follow census block boundaries. They are not required to follow block group, census tract or other census geographies. Unique ZIP Codes specifically created for individual corporations or organizations are excluded for ZCTA purposes, but a ZIP Code for a commercial district may be used for ZCTA creation and naming if it covers the majority of the addresses of the census blocks in an area. The process of assigning blocks to ZCTAs is a fully automated process based on addresses at the time of the census. ZCTA boundaries are, therefore, not stable over time.
Census blocks having no addresses, islands and unassigned blocks are assigned to the nearest ZCTA to provide complete area coverage. ZCTAs are named for the five-digit U.S. Postal Service ZIP Code that is most common to the addresses within the ZCTA. Large, undeveloped areas are assigned the three-digit ZIP Code. Census blocks covering large bodies of water are assigned a three-digit ZIP Code followed by "HH".
ZCTA boundaries are available on Census 2000 TIGER/Line files, and users may create tables and plot ZCTA maps on American FactFinder.