There are separate pages for each the main periods for which different constituency boundaries existed:
1918 - 1950 (note that the Special Review of abnormally large constituencies implemented in 1945 did not affect Wales)
These maps have been created by the author of this website working backwards in time from the current boundaries. The data for 2010 and 2024 boundaries is sourced from Ordnance Survey Open Data and permission to use this is gratefully acknowledged.
Hovering over any map will reveal the constituency name (in the same format as used in the rest of this site) - this will be centred within the constituency, but clicking on the map will show the constituency name at the point clicked.
If you wish to download the data to use in your own application you may do this using the share icon towards the top left of the map. This gives an option for data download, in a variety of formats. Using geojson, for example, should allow the data to be imported into a GIS and reformatted as required. If you do reuse this data please ensure that you credit parlconst.org as the source.
Care has been taken in producing and checking these maps. However, given the scale and nature of the project it is almost inevitable that there may be some errors. Should anything be found which doesn't look right, please get in touch using the contact form, so that it may be corrected.