Also known as Chapman Codes
The County or Chapman Codes were devised as simple abbreviations for use in genealogical (family history) research and the like by Dr Colin Chapman. Others saw the advantage in using them and have since used them more widely. When an internationally recognised set of codes were required, these were expanded and the ISO 3166-2:GB and BS 6879 codes were produced. Although an expanded set is available, many people like to continue to use the far simpler and easier to remember set that is of use to people undertaking local history and genealogical (family history) research, rather than a code set that may be more suitable for accounting purposes within government.
Prior to this, from around 1923, when the 'Place Names Society' was formed, a set of abbreviations existed ranging from 1 to 3 letters, this was expanded in a number of ways by different organisations over the years but with the coming of computers and the potential for the sharing of data there was the need to standardise on one set.
Colin Chapman, in around 1979, started with the set produced by the 'Place Names Society' and converted them into a three letter code set, by taking the existing code and expanding it in a way that was least likely to be confused with any other, and adding new codes for the later counties that had been established. These then became the widely used set. With many of us expanding the set slightly, adding a few unofficial codes to meet our needs.
The Chapman County Code was used in 1987 by the British Standards Institution as the basis for the preparation of British Standard 6879 and revised again in 1999, and by the International Standards Organisation in Geneva when publishing ISO 3166-2.
ISO 3166-2 expanded this further adding unitary authorities and other county and region areas. They also prefix the Chapman County Codes list with a GB-, so for example, Cheshire in Chapman Code is CHS and the ISO 3166-2 its GB-CHS. This allowed it to go international and include both all administrative districts and different structures, in some countries there are in excess of 4000 sub divisions, while others, for example Ghana has just 10 regions. In relation to the UK there has been at least 3 sets of changes to the ISO code set.
The ISO code set is very large, even the UK set is larger than most people need, as many towns that are unitary authorities have their own codes. While the ISO set is useful for Government administration and accounting, most people will find the original set is large enough, and importantly is static, so data does not have to be changed.
The County Code List we have produced is the straight forward Chapman County Code list, without additions or alterations.
Some versions, at least, of the Microsoft Windows Operating Systems, will not allow you to create a directory called CON, the Chapman Code for Cornwall, and to overcome this an alternative code COW is used by some of us.
The other expansion that we have found we have needed for some projects is a regional one, for example a code for South Wales, West Country, or Lake District, as well as for short lived counties like Avon where there is no code. These are not a part of the standard code set and if you introduce any yourself then the data is not necessarily fully compatible with that used by others. But as nearly exclusively we are creating data sets for our own use this is of less importance, we try to minimise the number of non standard codes that we use.
If adding your own codes just first check the alphabetic list of codes to make sure the code you are about to use is not already in use.
The problem of moving boundaries
Governments are constantly messing about with boundaries, joining things together and chopping them apart. While the policy of constant change may suit politicians it makes it very difficult to classify anything by an area, especially where the data is coming from across a long period in time. The postal address has not helped as often this is relating to the postal town not its location, and from 2013 county's are being removed form the postal address file.
Generally, where we can, its better to convert all material to a standard set of areas and in our case we use the ceremonial counties, as their boundaries don't shift about. These conveniently also line up with the county code list. You can see the ceremonial counties mapped in our County Index plus we have two other articles Introduction to Locations by County and The History of How Counties Came About.
Lochin Publishing - Colin Chapman's publishing and lecture company