There are separate pages for each the main periods for which different constituency boundaries existed:
1922 - 1950 (note that the Special Review of abnormally large constituencies implemented in 1945 did not affect Northern Ireland)
1950 - 1974 (note that the First Periodical Review recommended no change in Northern Ireland constituencies)
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 the Ordnance Survey of Northern Ireland and permission to use this is gratefully acknowledged. Also, thanks to obsie for sharing his work on the Irish constituency boundaries that were implemented in 1885 and 1918.
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. Due to difficulties in obtaining good historical maps for Northern Ireland, there is less confidence about the accuracy of some of these constituency maps than for other parts of the United Kingdom. Should anything be found which doesn't look right, please get in touch using the contact form, so that it may be corrected.