Partition of Ireland
The partition of Ireland () divided the island of Ireland into two distinct jurisdictions, Northern Ireland and Southern Ireland. It took place on 3 May 1921 under the Government of Ireland Act 1920. Today the former is still known as Northern Ireland and forms part of the United Kingdom, while the latter is now a sovereign state also named Ireland and sometimes called the Republic of Ireland.
Dioceses of Ireland
The pre-Reformation Christian church in Ireland was first divided into dioceses at the Synod of Ráth Breasail in 1111, although the dioceses of Dublin and Waterford were founded earlier by Hiberno Norse rulers with bishops consecrated by the Archbishop of Canterbury in England. The boundaries were reconfigured at the Synod of Kells in 1152 into 37 dioceses. A few were later abolished, as when Glendalough merged Dublin in 1214–16.