This data set is available at any of the following levels of geography:

• Nation
• States
• MSAs
• Counties
• Places (Cities)
• MCDs (Towns, Townships)
• Tracts
• Block Groups
• Zip Codes

Zip code definitions come from at least two different federal agencies and they don't always line up perfectly. The data in this product defines zip codes using the US Postal Service (USPS) definitions. But the geographic boundaries are derived from the Census Bureau's (USCB) Tiger files and are officially Zip Code Tabulation Areas (ZCTA). Most of the time these two are relatively in accord. But there are some differences. For example the USPS has zip codes for PO Boxes. The USCB does not - no one "lives there" though many people may receive mail there and it is an official mailing address. Also the USCB seeks to cover the entire country so for example it will assign NY City's Central Park or Yosemite to a zip code. The USPS may not include these areas because in fact they are not official mailing addresses.