Monday, 24 January 2011

Zip Codes and Postcodes

In Britain we have postcodes. The postcode for the House of Commons is SW1A 0AA. The SW is the postcode area. (other examples are NN - Northampton area; MK - Milton Keynes area; WS - Walsall area; LE - Leicester area). The 1A is the postcode district within the area. (I live in MK4, I grew up in WS9). Each district is subdivided into sectors (BBC Northampton is in NN1 2). The final two letters are the smallest unit  (known as the postcode unit )- and may represent a single street, part of a street or even an individual building. (The Palace of Westminster has AA for the Commons and PW for the Lords).

Zipcodes in the US are numeric - the basic unit has five numbers - which can cover an area as small as the Senate (20510) and the House of Representatives (20515)

The first three numbers are the Sectional Center Facility - which is the central mail processing facility for that area. The first number represents a number of states (Primary State Prefix), the second and third a region withinn the area designated by the first number (SCF). The final two digits (local zip) represent sorting areas, which may be a city or town, part of a city or town, or a smaller settlement. 

I spent the last week in 20015 and am now in 22308 (can you work out where?). In order to give a more precise location there is "ZIP+4", this may be as small as a city block. The zipcode for Politics and Prose is 20008-2024.

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