Zip Code Maps
Zip Code Mapping
The ZIP code orientation in the U.S. seems random. Not only do boundaries change regularly based on delivery needs of the Postal Service, but these codes don't actually relate to areas of land; they primarily relate to delivery routes (e.g. roads). Some buildings have a unique ZIP Code, and some large buildings may even have a different ZIP Code for each floor! A Postal Service station, where post office boxes can be rented, may have its own ZIP code. Recently, with the use of data visualization techniques, animated maps can display this seemingly random web into an ordered, readable map (Ben Fry 2004).
Postal Service Data
The Postal Service does not maintain ZIP Code maps, and the only related product available at this time is the TIGER/ZIP+4 File. This file relates ZIP+4 codes to Census Bureau data (e.g. latitude, longitude, tract, Standard Metropolitan Statistical Area (SMSA), etc.) See http://zip4.usps.com/zip4/welcome.jsp.
Census ZCTAs
Another option is to rely on a product from the Census Bureau based on what are called Zip Code Tabulation Areas (ZCTAs). The ZCTAs use Census blocks as their aerial basis to overcome the operational difficulties of creating a well-defined ZIP Code area. ZCTAs were developed for the first time in conjunction with the 2002 Census. See www.census.gov/geo/ZCTA/zcta.html.
There is no direct correlation between Postal Service ZIP Codes and Census Bureau geography. This is because individual Postal Service ZIP Codes can cross state, place, county, census tract, block group and census block boundaries(just to name a few). The geographic entities the Census Bureau uses to tabulate data by are relatively stable and over time. For instance, census tracts are only defined every ten years.
In contrast, U.S. Postal Service ZIP Codes are designated to meet the day-to-day operational needs of the U.S. Postal Service and tend to change more frequently than every ten years. Because of the ill-defined nature of ZIP Code boundaries, the Census Bureau does not have a file (crosswalk) showing the relationship between U.S. Census Bureau geography and U.S. Postal Service Zip Codes.
Obtaining Zip Code Maps
Until recently, zip code maps have only been available in printed format. The most common source of maps are local zip code boundaries published in local telephone directories. However, there are now several zip code directories published and available to the public. For digital zip code data that can be used in a GIS, extracts from the U.S. Census Bureau's TIGER database are currently available.
The National 5-digit Zip Code and Post Office Directory, published by the National Information Data Center, has maps of zip code areas and listings that are referenced by zip codes for state, city, and street. The directory is updated yearly and usually costs around $39.00.
The Zip Code Map of Wisconsin contains information on the 5-digit zip codes of cities, towns, and regions in the state. The map is published with a scale of 1" to 14 miles, and measures 25" x 40". The latest version is for 1995 and reflects the most recent changes. The map costs $25.00, or for a laminated copy $50.00. For further information contact Milwaukee Map Service.
Rand McNally & Company publishes the Zip Code Data Atlas, an ideal reference for routing and marketing in U.S. territories. Each state is divided into zip code regions, and listings of counties and towns, population data, and categorical rankings are also included. This atlas sells for $29.95 and is available from Rand McNally & Company.
The website http://www.batchgeocode.com/ provides a useful application for zip code lookup. Either by entering a single address/zip code or submiting an address list from a spreadsheet, the service returns the geographic coordinates of the location(s) and shows the area on a web map. The results can also be downloaded into Google Earth, saved to a web page, or transferred back into a spreadsheet.
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