1885–1918: In the Borough of Belfast, that part of Dock ward bounded on the south-east by a line drawn along the centre of North Queen Street, on the north-east by a line drawn along the centre of New Lodge Road, on the south-west by a line drawn along the centre of Limestone Road and York Road, and on the east by a line drawn along the centre of Carrickfergus Road, and that part of St. Anne's ward not in the constituency of Belfast West, and the townlands of Ballygomartin, Ballysillan Lower, Greencastle, Legoniel, Lowwood, Old Park and Skegoneill in the parish of Shankill, along with that part of the townland of Ballyaghagan within the parliamentary borough.
1922–1974: The County Borough of Belfast wards of Clifton, Duncairn, and Shankill.
1974–1983: The County Borough of Belfast wards of Clifton, Dock, Duncairn, and Shankill.
1983–1997: The District of Belfast wards of Ardoyne, Ballysillan, Bellevue, Castleview, Cavehill, Cliftonville, Crumlin, Duncairn, Fortwilliam, Grove, Legoniel, New Lodge, Shankill, and Woodvale.
1997–2010: The District of Belfast wards of Ardoyne, Ballysillan, Bellevue, Castleview, Cavehill, Chichester Park, Cliftonville, Crumlin, Duncairn, Fortwilliam, Legoniel, New Lodge, Water Works, and Woodvale, and the District of Newtownabbey wards of Abbey, Coole, Dunanney, Valley, and Whitehouse.
2010–present: The District of Belfast wards of Ardoyne, Ballysillan, Bellevue, Castleview, Cavehill, Chichester Park, Cliftonville, Crumlin, Duncairn, Fortwilliam, Legoniel, New Lodge, Water Works, and Woodvale, and the District of Newtownabbey wards of Abbey, Ballyhenry, Cloughfern, Collinbridge, Coole, Dunanney, Glebe, Glengormley, Hightown, Valley, and Whitehouse.
The seat was recreated in 1922 when, as part of the establishment of the devolved Stormont Parliament for Northern Ireland, the number of MPs in the Westminster Parliament was drastically cut. The seat is centred on the north section of Belfast, though at times the area around the Docks on the north side of the Lagan Estuary has instead been part of variously Belfast East and Belfast West. Belfast North also contains part of the district of Newtownabbey.
At the boundary commission hearings in September 2005 prior to the 2010 general election, the SDLP proposed extending the seat to Cloughfern and Jordanstown. The DUP supported the addition of Cloughfern. Sinn Féin were generally supportive of the commission's proposals.
Following the revised recommendations, the Commission proposals were finalised and accepted by Parliament through the Northern Ireland Parliamentary Constituencies Order.
Belfast North is a constituency with a nationalist majority. Belfast North historically had a narrow unionist majority, which gradually decreased over time. The nationalist vote is considerable, and those from a Catholic background (47%) now slightly outnumber those from a Protestant background (46%), according to the 2011 census. It has generated particular interest for a number of highly unusual election results, as well as for several candidates and MPs prominently disagreeing with their parties.
The area saw a steady out movement of Protestants during the Troubles, to some degree replaced by a growing Catholic population, although the overall population of the area fell sharply. However, all the inner-city communities in the constituency are now haemorrhaging electors, and the overall ethnic composition of the constituency now seems stable.
The seat was consistently held by the Ulster Unionist Party from its creation until the 1970s. In 1972 the first notable dissent occurred when the sitting MP, Stratton Mills, dissented from the UUP's decision to withdraw from the Conservative whip at Westminster over the suspension of the Stormont Parliament. Mills remained as a Conservative MP, but the following year he joined the Alliance, giving them their only Westminster representation before 2010.
The 1979 general election saw one of the most dramatic results of all when Johnny McQuade of the Democratic Unionist Party won the seat with a mere 27.6% of the vote – the third lowest total for a successful candidate in a UK general election in the twentieth century. This came about due to the strong showing of several other parties, dividing the vote strongly. McQuade also had the distinction of being the oldest person to be initially elected to Westminster in the 20th century and did not stand at the next general election.
Walker continued to hold the seat until 2001 but gained a reputation for inactivity. In the 2001 general election the DUP contested the seat for the first time since 1983, with their candidate Nigel Dodds campaigning heavily on both their opposition to the Good Friday Agreement and Walker's record. Walker also suffered from a disastrous television interview during the campaign. In the election Walker's vote collapsed to a mere 12%, coming fourth whilst Dodds won the seat. The UUP vote fell even further in both the 2003 Assembly election and the 2005 general election.
Nigel Dodds became the DUP's deputy leader and Commons leader in 2008, but the 2010 general election saw Sinn Féin increase their vote share and reduce the DUP majority. Sinn Féin targeted the seat in the 2015 general election, campaigning on returning the constituency's first Irish nationalist MP and the growing Catholic population surpassing Protestants. However, the DUP and the UUP agreed an electoral pact in which the UUP would withdraw their candidate to help re-elect an unionist. This allowed for Dodds to hold the seat comfortably with an increased majority, although a 4.3% swing to Sinn Féin in the 2017 general election still confirmed the seat's marginal status.
Prior to the 2019 general election, the SDLP and UUP withdrew their candidates. In a highly divisive contest marred by threats from loyalist paramilitaries, John Finucane of Sinn Féin won with a majority of 1,943 votes. This meant that the 2019 election was the first time that Sinn Féin won multiple seats in Belfast and the first time Belfast North had elected a nationalist instead of a unionist. Dodds was replaced as Commons leader by Jeffrey Donaldson.
^"Usual Resident Population". Northern Ireland Neighbourhood Information Service. Northern Ireland Statistics and Research Agency. Archived from the original on 23 September 2021. Retrieved 26 January 2015.