Postal district

A postal code (also known locally in various English-speaking countries throughout the world as a postcode, post code, Eircode, PIN Code or ZIP Code ) is a series of letters and/or digits, sometimes including spaces or punctuation, included in a postal address for the purpose of sorting mail.

In February 2005, 117 of the 190 member countries of the Universal Postal Union had postal code systems.

Although postal codes are usually assigned to geographical areas, special codes are sometimes assigned to individual addresses or to institutions that receive large volumes of mail, such as government agencies and large commercial companies. One example is the French CEDEX system.

There are a number of synonyms for postal code; some are country-specific.

The development of postal codes reflects the natural evolution in which postal delivery grew more complicated as populations grew and the built environment became more complex. This process occurred first in large cities. The nucleus of a postal code idea thus began with postal district numbers (or postal zone numbers) within large cities. London was first subdivided into 10 districts in 1857, and Liverpool in 1864. By World War I or possibly earlier, such postal district or zone numbers existed in various European large cities. They existed in the United States at least as early as the 1920s, possibly implemented at the local post office level only (for example, instances of "Boston 9, Mass" in 1920 are attested), although they were evidently not used throughout all major US cities (implemented USPOD-wide) until World War II.

By 1930 or earlier the idea of extending postal district or zone numbering plans beyond large cities to cover even small towns and rural locales was in the air. This was the concept that would create postal codes as we define them today. (The very name of US postal codes, "ZIP codes", reflects this evolutionary growth from a zone plan to a zone improvement plan [ZIP].) Modern postal codes were first introduced in the Ukrainian Soviet Socialist Republic in December 1932, but the system was abandoned in 1939. The next country to introduce postal codes was Germany in 1941, followed by Argentina in 1958, the United States in 1963 and Switzerland in 1964. The United Kingdom began introducing its current system in Norwich in 1959, but completed the nationwide introduction in 1974 only.

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