Townlands
When researching your family history, it is important to find out the name of the townland where your ancestor lived. A townland is the smallest administrative unit in Ireland. It is an old Gaelic subdivision which predates the Norman invasion of 1169. Knowing the county or parish of an ancestor may not be sufficient. It is likely that your family name will occur many times in any given county or parish. The townlands of Ireland are listed and displayed on a map at Ordnance Survey of Ireland.
Parishes
The next biggest unit is the parish, and this is a potential source of confusion. There are broadly speaking, two types of parish. There are ecclesiastical parishes which are run by the different churches e.g. Roman Catholic, Church of Ireland etc, and there are civil parishes. The civil parishes are the parishes which pre-date the Reformation in Ireland and were sometimes used by the British authorities in Ireland. For example, the civil parishes were used by the two resources which were created for the purposes of taxation and which are discussed later in this site, i.e. Griffith's Valuation and the Tithe Applotment Books. Initially, the Church of Ireland parishes were based on these pre-reformation parishes, but after this church's disestablishment in 1869, the boundaries of its parishes could be altered without affecting the boundaries of the civil parish on which it was based.
In a great many cases the Roman Catholic parish, the Church of Ireland parish, and the civil parish in which a townland is located will all bear the same name, but you should be mindful that this will not always be the case. Sometimes, you will know the church parish and not find a corresponding civil parish when searching through Griffith's Valuation or the Tithe Applotment Books. Generally, if an emigrant provides a parish name as his or her parish of origin, this is a church parish. A corresponding parish may not be found in Griffith's Valuation or the Tithe Applotment Books, because as already stated, these are based on the civil parish which may not be the same as the church parish. Throughout this web page when the word parish is used, the type of parish will always be specified.
District Electoral Divisions
District Electoral Divisions are used in the 1901 and 1911 Census. The census groups townlands into DEDs. It is not necessary to know the DED to search each census. It is possible to search by family name.
Baronies
Parishes (both civil and church) are grouped into baronies. The barony does not feature prominently in genealogical research.
Baronies are grouped into counties.
Registration Districts
Finally, the Registration District is used in the civil registrations of births, marriages and deaths. Civil registration began in Ireland in 1864. It is unlikely that you will know the registration district, but it is relatively easy to find out this information, and then use it in subsequent searches.