According to Official Guinness Records,
The earliest code used in a postal system was introduced in London, England, in 1857 by Sir Rowland Hill (UK). The code divided London into postal districts based on compass points - ‘N’ for North, ‘S’ for South, etc. The present form of the postcode - a mixture of letters and numbers that can be decoded by machine to allow faster sorting - was first used in Norwich, UK, in October 1959. The similar zip code came into use in the USA in July 1963.
For a complete list of 1857 records, please visit 1857 Guinness Records in United Kingdom.