A number of online sources generate lists of all cities within a ZIP code, including USPS.com, UnitedStatesZipCodes.org, Zip-Codes.com and MelissaData.com. Some of these sites also provide geographic information and demographic data for those cities.
The United States Postal Services website, USPS.com, generates a list all cities within a ZIP code. A ZIP code search on UnitedStatesZipCodes.org or Zip-Codes.com produces a city list together with maps and demographic data, including population and census information for listed cities. MelissaData.com generates a list of cities within a ZIP code and links to city maps and demographic data, including information on schools and real estate prices.