Dublin 3

Dublin postal districts have been used by Ireland's postal service, known as An Post, to sort mail in Dublin. The system is similar to that used in cities in Europe and North America until they adopted national postal code systems in the 1960s and '70s. These were incorporated into a new national postcode system, known as Eircode, which was fully implemented in 2015. Under the new Eircode system, the Dublin Region incorporates the original routing areas D01 to D24, along with new A## and K## codes for the remainder of the county.

The postal district system was introduced in 1917 by the British government, as a practical way to organise local postal distribution. This followed the example of other cities, notably London, first subdivided into ten districts in 1857, and Liverpool, the first city in Britain or Ireland to have postcodes, from 1864. The letter "D" was assigned to designate Dublin. The new Irish government retained the postal district system, but district numbers were not used by the public until 1961, when they were added to street signs. Prior to 1961, street signs only displayed the street name in Irish and English.

The number of districts was increased as the city grew, and in the 1970s, large districts were subdivided. Dublin 5 was split, with the coastal part retaining the "5" and the inland part becoming Dublin 17. Dublin 8, Ballyfermot, one of the city's fastest growing suburbs, became Dublin 10, along with Palmerstown and Chapelizod. However, Dublin 10 was subsequently split again, with Palmerstown and Chapelizod forming Dublin 20.

In 1985, Dublin 6 was divided, with some areas, such as Templeogue, Kimmage and Terenure becoming part of a new district in order to facilitate processing of mail by a new delivery office for those areas. Residents of some areas objected to the assignation of the next available number, "Dublin 26," for the new postal district, citing property devaluation: the higher numbered districts typically represented less affluent and less central areas. An Post ultimately relented, and the district became known as Dublin 6W. However, the eastern half of the old D6 postcode area remained "Dublin 6" rather than "Dublin 6E".

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