The following site has a list of all country codes.
Overview of the codes
In 1923, the English Place Name Society was established and a series of abbreviations was produced for the counties in existence at that time. Many of these consisted of only one or two letters. In 1973, the Society of Genealogists (SOG) extended this system to cover the other counties in the British Isles.
Over the years the post office and other authorities had been using other standards for abbreviating county names. With the creation of new counties and amalgamation of others in1974, the abbreviations multiplied. The foundation of the Federation of Family History Societies (FFHS) in 1974 brought together many individuals and groups all having an interest in using abbreviated county names, with many of these groups using a different system.
The advent of computers and the need for standardisation led to the creation of the Three Letter Coded System for each of the counties in the British Isles. Where possible the systems proposed and used by the English Place Name Society and SOG were retained and where necessary the abbreviations extended to three letters.
This might not always produce the most logical abbreviation, as the three letters chosen may have already been allocated to another county and therefore some modification was necessary. The post-1974 counties have been included in the current listings.
Colin Chapman, a previous Vice-President of the FFHS was responsible for introducing the present County Codes and over time they have become universally known as the Chapman County Codes. This system has now been incorporated into the British Standard Specification and the Chapman Codes have been extended to include not only the codes for the UK but also for overseas countries.
A list of the codes for Australia and New Zealand, the countries of the British Isles (England and adjacent islands, Ireland, Scotland and Wales), as well as countries World Wide is provided. This listing may or may not include all countries/territories, but should provide the researcher with a reasonably comprehensive listing.
Also included is a list of ISO3166-2 Codes for states of USA and provinces of Canada, used in genealogy.
As well as country or county codes, there are several general codes:
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