| The US Postal Service uses zipcodes as part of the | | | | additional four digits are used to identify a geographic |
| addresses so that it can direct the mail to the | | | | region. The code is transferred to a bar code which |
| appropriate person. The ZIP part of the word is an | | | | the sorting machinery used in the post offices can |
| acronym for Zone Improvement Plan. The basic | | | | use to make sure the mail goes to the appropriate |
| format of all zip codes consists of five numbers, In | | | | locality. For addresses with post office boxes, the |
| 1983 a ZIP + 4 format was introduced, which | | | | add on digits refer to the post office box number. |
| consists of the basic five numbers, a hyphen and | | | | However, unlike the regular zip codes for cities, there |
| then four more numbers. | | | | is no uniform code for post office boxes. If you |
| The process of using zip codes for pieces of mail in | | | | want to send mail to a particular address you would |
| the US started in 1943 when the US Post Office | | | | have to look up the full 12-digit zip code. |
| started using codes to identify large cities within | | | | The first digit of the zip code represents a |
| states. This was the brainchild or a postal worker, | | | | geographical area of the country, such as a group of |
| Robert Moon, who submitted his proposal to the | | | | states. Together with this digit and the next two, the |
| Postal service in 1941. A more general system was | | | | mail goes to the appropriate facility where the mail is |
| introduced in the early 1960's and a zip cods for the | | | | sorted once again. The fourth and fifth digits of the |
| entire country came into effect in 1963. Moon's | | | | zip code refer to the addresses within a specific |
| proposal was to use three digits to identify each | | | | region. Usually the main city in a region receives the |
| sectional center facility in the country and this | | | | first zip code and then the surrounding towns and |
| system is still in effect. The five digits consist of the | | | | cities receive zip codes in alphabetical order following |
| number for the sectional facility and the postal code | | | | that initial zip code according to the name of the city |
| for the city in the state. For example the zip code | | | | or town. |
| for Aaronsburg, Pennsylvania is 16820. The numbers | | | | Most of the lowest zip code numbers are in the New |
| 168 refer to the sectional center facility and the | | | | England states, since they all start with 0. Other |
| numbers 20 refers to the postal code for | | | | postal codes beginning with 0 are the US Internal |
| Pennsylvania. | | | | Revenue Service, Adjuntas, Puerto Rico and cities |
| In 1963, zip cods were only used for first class mail | | | | starting with A in this region. New York State has the |
| and it wasn't until 1967 that packages and second | | | | initial digit of 1, so the zip codes of all addresses in |
| and third class mail were required to use them in the | | | | New York start with 1. |
| addresses. In the ZIP + 4, system now in use, the | | | | |