The U.S. Census Bureau provides statistical data and geographic products for census blocks grouped into ZIP Code Tabulation Areas (ZCTAs) at Census.gov. The Census Bureau assigns ZCTA codes to groups of census blocks based on the most commonly occurring ZIP code in each area.
Many areas have the same ZCTA code as ZIP code, but ZIP codes with few addresses may not have corresponding ZCTA codes. The Census Bureau determines ZCTA codes after each decennial census. Statistical data from the 2000 and 2010 censuses and the 2007-2011 American Community Survey are available by ZCTA code through the American FactFinder. The data can be found by performing an advanced search narrowed by geography.