Its geographical remit straddles two civil jurisdictions: in Northern Ireland, it covers all of County Londonderry and large parts of County Tyrone while in the Republic of Ireland it covers County Donegal.
The English-speaking minority mostly adhered to the Church of Ireland or to Presbyterianism, while the Roman Catholic Church undertook extensive mission work and retained the allegiance of the majority of the population in Ireland as a whole.
From the 1830s onwards, many Anglican dioceses were merged, in view of declining membership.
The sees of Derry and Raphoe were united in 1834.
[1] It is for this reason that the united diocese has two cathedrals.