The following provinces of Ireland are significant in historical research of surnames and for the most part have survived the centuries as they were once held.
Connaught is the westernmost province of Ireland. In the modern era, the has been spelling changed to Connacht. This province has a population of approximately 424,000 today, and contains the counties of Galway, Leitrim, Mayo, Roscommon, and Sligo. These county names have remained the same since the Middle Ages.
Leinster is in the southeast of Ireland, and is the most populous of the four provinces, with approximately 1,500,000 people. This province contains the counties of Carlow, Dublin, Kilkenny, Laois (formerly Leix), Longford, Louth, Meath, Offaly, Westmeath, Wexford, and Wicklow. These divisions have remained the same from the Middle Ages to the present.
Munster is the southernmost of the four Irish provinces. As of 2006, it has a population of 1,172,170 people, and contains the counties of Clare, Cork, Kerry, Limerick, Tipperary, and Waterford. These districts have remained unchanged since the Middle Ages.
Cork is the largest city with a population of 190,384 (2006). In the 2006 census, Limerick had a population of 90,757 and Waterford had a population of 49,213.
The northern region of Ulster was an ancient kingdom, and one of the four historic Provinces of Ireland. The region was mostly annexed by the English Crown during the reign of James I (1603-1625).
In the Middle Ages, the Province of Ulster contained the counties Donegal, Derry, Antrim, Down, Armagh, Cavan, Monaghan, Fermanagh, and Tyrone.
The Province of Ulster is now divided between The Republic of Ireland, and Northern Ireland, which is often referred to as Ulster. Northern Ireland is a political division of the United Kingdom; it is made up of the counties Antrim, Armagh, Down, Fermanagh, Derry, and Tyrone .
The 26 districts present day Northern Ireland are: Antrim, Ards, Armagh, Ballymena, Ballymoney, Bainbidge, Belfast, Carrickfergus, Castlereagh, Coleraine, Cookstown, Craigavon, Down, Dungannon, Fermanagh, Larne, Limavady, Lisburn, Londonderry, Magherafelt, Mourne, Moyle, Newtownabbey, North Down, Omagh, and Strabane.