The constituency was created in 1921 as a 6-seat constituency, under the Government of Ireland Act 1920, for the 1921 election to the House of Commons of Southern Ireland, whose members formed the 2nd Dáil.
Under the Electoral Act 1923, it became an 8-seat constituency for the 1923 general election to the 4th Dáil. It remained at that size until major boundaries changes for the 1937 election to the 9th Dáil, when its geographical area was reduced and its representation cut to 5 seats.
Throughout its history the constituency consisted primarily of the area of County Dublin, excluding the area of Dublin city. However, at various points it also included some territory from within the boundaries of Dublin City, which were expanded under the Local Government (Dublin) Act 1930.[1]
1921–1923 (6 seats)
The boundaries covered all of County Dublin, excluding the area within Dublin city
1923–1937 (8 seats)
Under the Electoral Act 1923, the boundaries of the constituency were defined simply as "the administrative county of Dublin",[2] that is County Dublin excluding the area within the boundaries of Dublin city. These boundaries took effect at the 1923 general election.
1937–1948 (5 seats)
The Electoral (Revision of Constituencies) Act 1935 followed the removal from the county to the city of heavily populated suburbs from former Pembroke Township. Most of those areas became part of a new 3 seat Dublin Townships constituency, but some wards which had become part of the city remained within the county constituency. The 1935 Act defined the new boundaries of the constituency as "The administrative County of Dublin. The following townlands or portions of townlands comprised in the County Borough of Dublin: Annefield, Crumlin, Kimmage (parish of Crumlin), Kimmage (parish of Rathfarnham), Larkfield, Newtown Little, Priesthouse, Rathfarnham, Saint Lawrence, Simmonscourt, Stannaway, Terenure and Tonguefield".[3] These boundaries took effect at the 1937 general election.
1948–1961 (3 seats)
The Electoral (Amendment) Act 1947 reduced the size of the constituency, removing most of the areas within the boundary of Dublin city, and removing a further substantial area in the south of the county to form the new Dún Laoghaire and Rathdown constituency. A further area in the North–East of the county, from Killester to Malahide to Howth, was removed to a new Dublin North-East constituency. The boundaries were formally defined as "The Beann Eadair ward and the administrative county of Dublin except the portion thereof which is comprised in the county constituency of Dun Laoghaire and Rathdown and the portion thereof which is comprised in the borough constituency of Dublin North (East)".[4] These boundaries took effect at the 1948 general election.
1961–1969 (5 seats)
The Electoral (Amendment) Act 1961 expanded the constituency boundaries again, restoring the areas which had been removed to Dublin North-East and adding part of Ballyfermot. The new boundaries were defined as "The administrative county of Dublin, except the part thereof which is comprised in the county constituency of Dun Laoghaire and Rathdown; and the part of the Ballyfermot ward in the county borough of Dublin which is not included in the borough constituency of Dublin South-West."[5] These boundaries took effect at the 1961 general election.
Note: The columns in this table are used only for presentational purposes, and no significance should be attached to the order of columns. For details of the order in which seats were won at each election, see the detailed results of that election.
A by-election was held on 18 February 1926 to fill the seat in the 4th Dáil which had been vacated by the death of the independent TD Darrell Figgis. It was won by the Labour Party candidate William Norton. Norton's win was the first by a Labour Party candidate at any by-election since the establishment of the First Dáil. Labour did not repeat Norton's feat of winning a seat from another party in a by-election for 72 years, when Seán Ryan won the Dublin North by-election in March 1998.
In the 1921 general election to the 2nd Dáil, no constituencies were contested. As in other constituencies, all 6 candidates in Dublin County were returned unopposed.
^ abcdefghijklmnopqrstuWalker, Brian M, ed. (1992). Parliamentary election results in Ireland, 1918–92. Dublin: Royal Irish Academy. ISBN0-901714-96-8. ISSN0332-0286.
^ abcGallagher, Michael (2009). Irish Elections 1948–77: Results and Analysis Sources for the Study of Irish Politics 2. Routledge. ISBN9781138973343.
^ abWalker (1992) lists the size of the electorate in Dublin County as 110,840 in June 1927 and 100,840 in September 1927. The scale of difference in such a sort period of time and the fact that difference is a exactly 10,000 suggests that one or other of these figures may be the result of a typographical error.