[3] Continuing unrest resulted in the Anglo-Irish Treaty and the Provisional Government, which administered Southern Ireland from 16 January 1922 to 5 December 1922: effectively a transitional administration for the period between the ratifying of the Anglo-Irish Treaty and the establishment of the Irish Free State.

Many unionists feared that a nationalist government in Dublin would impose tariffs that would unduly burden the north-eastern counties of the province of Ulster, which were not only predominantly Protestant but also the only industrial area of a largely agricultural island.

One of those most opposed to this partition settlement was the leader of Irish unionism, Dublin-born Sir Edward Carson, who felt that it was wrong to divide Ireland in two, and felt this would badly affect the position of southern and western unionists.

The first general election to the House of Commons of Southern Ireland in 1921, and the simultaneous general election to the House of Commons of Northern Ireland, was used by Sinn Féin to produce a single extrajudicial parliament, the Second Dáil.

When the new Parliament of Southern Ireland was called into session on 28 June 1921, only the four Unionist members of the House of Commons of Southern Ireland, and a few appointed senators, arrived in the Royal College of Science in Dublin, where the meeting was scheduled to occur; most of the other members met elsewhere as the Dáil.

The Provisional Government established by the treaty was constituted on 14 January 1922 at the above-mentioned meeting of members of the Parliament elected for constituencies in Southern Ireland.

Collins assumed charge of Dublin Castle at a ceremony attended by Lord FitzAlan.

With the establishment of the Irish Free State on 6 December 1922 by the terms of the treaty, Southern Ireland ceased to exist.