There are more than 42,000 ZIP Codes that designate delivery points within the United States and its territories, as well as the locations of its armed forces. ZIP codes are used not only for tracking of mail but can also be used to breakdown U.S. Census Data, Legislative Districts and Insurance Rates, to name a few. Download sales tax rates by ZIP code, here.
ZIP codes are a complex system of postal codes used by the United States Postal Service consisting of five numbers. An expanded ZIP+4 code, developed in the 1980s, includes the five main digits of the ZIP code, followed by a hyphen, and four additional digits that identify a geographic region within the five-digit delivery area, such as a particular city block, a grouping of apartment buildings, a single high-volume receiver of mail or any other entity that could use extra identification to aid in the efficient delivery and sorting of mail.
A brief history of the ZIP code:
1963: Non-required ZIP codes were defined for the entire United States.
1967: ZIP codes became required for second and third-class bulk mail and was later adopted for all mailing within the U.S.
1983: The USPS began using ZIP+4, often called “plus-four codes”, “add-on codes”, or “add ons”.
Quick Fact: In conjunction with the introduction of the ZIP code, two-letter state abbreviations were introduced.