BBC News By Luke Sproule became law. It partitioned Ireland into two separate jurisdictions - Northern Ireland and Southern Ireland. The latter would become the Irish Free State and eventually the modern Republic of Ireland. Northern Ireland would become the first part of the UK to have what we now call devolution. But what else did the Act contain? Northern Ireland and Southern Ireland In an attempt to reconcile the demands of unionists - the majority of whom lived in the north east of Ireland - to remain part of the UK and nationalists, most of whom by 1920 wanted full independence, the act split Ireland in two.