ZIP Code Geography and Mapping - 12/16/2003 GJH There are many, many websites that provide on-line services to calculate distances between ZIP Codes. Many commercial vendors provide ZIP Code data bases with address matching capabilities. The Census Bureau provides good information about the ZIP Code concept as it relates to mapping. The ZIP Code "area" is not designed as an actual polygon but instead is a collection of routes (transportation network), and they change often. Commercial companies have created ZIP Code boundary maps by interpolating the distances between instances of ZIP Codes on the ground (probably Post Office locations). The Census Bureau has been providing ZIP Code area centroids which is probably the dataset used in the distance calculation routines. To overcome this mapping difficulty, the Census Bureau has created the ZIP Code Tabulation Area (ZCTA) by using aggregations of Census blocks. But they warn that there is no correlation between the US Postal Service ZIP Codes and the US Census Bureau-created geography of those ZIP Codes. Each of datasets should be used with full knowldedge of their method of creation and intended uses. US POSTAL SERVICE ZIP Code Lookup and Address Information page http://www.usps.com/ncsc/ziplookup/lookupmenu.htm ZIP Code FAQ http://www.usps.com/zip4/zipfaq.htm ZIP Code lookup service http://www.usps.com/zip4/welcome.htm US CENSUS BUREAU ZIP Code information and FAQs http://www.census.gov/geo/www/tiger/tigermap.html#ZIP http://www.census.gov/cgi-bin/geo/tigerfaq?Q16 http://www.census.gov/cgi-bin/geo/tigerfaq?Q17 http://www.census.gov/cgi-bin/geo/tigerfaq?Q18 http://www.census.gov/cgi-bin/geo/tigerfaq?Q19 http://www.census.gov/cgi-bin/geo/tigerfaq?Q20 Census 2000 U.S. Gazetteer Files http://www.census.gov/tiger/tms/gazetteer/ http://www.census.gov/geo/www/gazetteer/places2k.html ZIP Code Tabulation Areas http://www.census.gov/geo/ZCTA/zcta.html http://www.census.gov/prod/2001pubs/mso01zcta.pdf 2000 5-Digit ZIP Code Tabulation Areas http://www.census.gov/geo/www/cob/z52000.html 2000 3-Digit ZIP Code Tabulation Areas http://www.census.gov/geo/www/cob/z32000.html text file of ZIP Codes and centroids http://www.census.gov/ftp/pub/tiger/tms/gazetteer/zips.txt http://www.census.gov/geo/www/gazetteer/newpagefiles/zip90r.txt 1990 ZIP Code file with lat/lon centroids http://www.census.gov/geo/www/tiger/zip1999.zip MISCELLANEOUS Zip Codes are Not Areas! http://exchange.manifold.net/manifold/manuals/5_userman/mfd50Zip_Codes_are_Not_Areas.htm As with most public domain data, there are many commercial enhancements and services created with specific uses of the data in mind. Here is just one such company: http://www.zipdatafiles.com/data/