Vision of Britain holds detailed data on every British election since 1832. The country was divided up geographically into constituencies, and we hold information about all the constituencies within Great Britain, including the different versions of their names. Most votes held in constituencies were as part of General Elections, when the whole country voted, but we also hold information on By-elections, when one or two constituencies voted because MPs had resigned, died, etc. Although today every constituency covers a well-defined geographical area, and elects just one MP, until 1950 there were also University Constituencies, whose voters were people who had graduated from a particular university, wherever they were living now. Until 1950, many constituencies elected two MPs, and some had as many as four. Vision of Britain is currently limited to Great Britain, but our data are all for elections to the UK Parliament at Westminster, so until 1922 the overall result of a General Election depended not just on the British results held here but also on voting in the whole of Ireland; from 1922 onwards, southern Ireland was a separate state but Northern Ireland still sends MPs to Westminster.
These other rates are also available for this theme but cannot be mapped for modern units: