zip codes

ZIP stands for zone improvement plan. There are 41,716 codes in United States of America.

Robert A. Moon, a postal employee, noted that rail based and address based delivery systems would not scale and fought for twenty years for number based systems what was to become the ZIP code with three digits. He divided the country into 900 regions.  H. Bently Hahn added fourth and fifth digits and persuaded the panel to go with five digits and credited with new system that revolutionized the postal delivery. It is further extended to nine digits or zip+four system in 1983.

Before zip codes were invented, workers sorted mail in some special mail cars in trains. United states post office (USPS) lost lot of trained personal during wars. Volume of mail was increasing rapidly - 43 million mails every week or 30 billion mails annually. Planes started carrying more mail than trains did.

The numerical system made easy transition to mechanized processing from manual sorting. However it took long time for people to start writing zip code along with mail address. United states post office (USPS) came up with cartoon character Mr. ZIP and campaigned that including zip code makes mailman travel with high speed. Mr. ZIP character was originally designed by Howard Wilcox of Cunnigham and Walsh Ad Agency for use by a Newyork bank to use in banking by mailing campaign. AT&T purchased the design and gave to USPS without the cost.

Some ZIP codes are unique to single high volume address like 20500 for white house and 72716 for Walmart headquarters. They are 2122 such codes. Some ZIP codes are for military, diplomat offices and embassies. There are 532 such codes. Some ZIP codes are used for solely post box addresses in some cities. There are 5122 such codes. Rest of the ZIP codes are based on geographical location. They are 29773 such codes.  Wealthiest zip code is 90210 for Beverly Hills, CA.

First digit denotes a state or group of states. The digit 9 is shared by west coast states California, Oregon and Washington, Alaska, Hawai and several other islands. Second and third digits denote a region or large city in those states. Together the first three digits denote sectional facility center or the main sorting and distribution center for an area. Fourth and Fifth digits denote group of addresses within a region. ZIP codes can cross state and other political boundaries. ZIP codes start on east coast and increase southwards and continue heading towards northward and westward east of Mississippi river, southward west of Mississippi river and northward on west coast.

ZIP codes are also used for gathering statistics like cenus data, marketing campaigns to identify purchase patterns, income patterns and demographics and as key in several online database systems.

References:
ZIP code
Robert Moon
H. Bently Hahn
wikipedia Mr. ZIP
USPS Mr. ZIP
Zip code statistics