Zip Code System in the United States
US Postal Service Zip Code System
Introduction to Zip Code System
In 1963 the ZIP (Zoning Improvement Program) code system was introduced to simplify the patterns and procedures of mail distribution. The ZIP code is a five-digit number used on the last line of the address following the name of the city and state. The first digit, from 0 to 9, stands for one of the ten main geographical areas into which the United States and its possessions are divided; each area includes three or more states or possessions. The next four digits delimit localities further by subdividing the main area; the first three digits together represent a sectional or metropolitan area, with the next two numbers specifying an associated or branch post office. In October 1983 the Postal Service began using an expanded ZIP code system of nine numbers, consisting of the five-digit code plus four additional digits, which specify an individual delivery route. Use of ZIP codes is voluntary; however, reduced postage rates are offered to large-volume mailers employing the expanded nine-digit code.” (1)
Resources
Notes and References
- Information about Zip Code System in the Encarta Online Encyclopedia