The Diocese was formed in 1111 at the Synod of Rathbreasail as the see for the Kingdom of Uí Chremthainn. The See was removed to Louth between 1135 and 1197, possibly to consolidate the power of the Bishop over against smaller Sees, before being returned to Clougher. At this time Louth was moved to the Diocese of Armagh, and the Ardstraw part of the diocese given to the Diocese of Derry. Church property that existed at the time of the Reformation, buildings included, was retained by the reformed Church of Ireland, then in the 19th century, at the time of the Disestablishment of the Church, confiscated by the state. Schools, churches and cathedrals were however returned to the Church. The diocese is unique within the Anglican Communion in having two diocesan cathedrals.