Alliance Party of Northern Ireland [SEP] inception
as official Opposition at Stormont, and the resignation of UUP Prime Minister of Northern Ireland Terence O'Neill in 1969, the NUM split between those who wished to remain a pressure group for the UUP and those who saw reform only through the establishment of a new political party. The latter broke off and formed the Alliance Party of Northern Ireland on 21 April 1970.
As Alliance viewed the situation, the major problem of Northern Ireland was the division between Protestant and Catholic. It contended that the turmoil had its origins in that division
The council was dominated by unionists from its inception until 1997, when they lost overall control for the first time in its history, with the Alliance Party of Northern Ireland gaining the balance of power between Irish nationalists and unionists. This position was confirmed in the three subsequent council elections, with mayors from the Irish nationalist Sinn Féin and Social Democratic and Labour Party (SDLP), and the cross-community Alliance Party regularly elected since 1997. The election in 2011 saw Irish nationalist councillors outnumber unionist councillors for the first time,