As in most genealogy research, you’ll need to know where your ancestors lived when you’re using records of Ireland. Try to learn the names of these jurisdictions for your ancestors:
The smallest civil geographic locality, similar to a neighborhood, the townland is the primary division in land surveys, such as Griffith’s Valuation. Townland names are often repeated in multiple parishes and counties. For example, Ireland has no less than seven townlands called Ballyadam: two in County Cork, two in County Limerick, and one each in counties Down, Waterford and Wexford. If you’re not sure of a townloand’s location, try searching here.
The parish is the organizational unit for Catholic church and Church of Ireland records, which are key to tracing family history before civil registration began in 1864. Both churches use parishes for administrative purposes, but they don’t necessarily use the same boundaries. Typically, Roman Catholic parishes cover wider geographical areas. Church of Ireland parishes are also referred to as civil parishes.
Poor Law Union
These unions were created in 1838 to administer relief to the poor.
District Electoral Division
Townlands were grouped into district electoral divisions (DEDs) for purposes of administering censuses. Several DEDs make up a civil registration district.
These county subdivisions are no longer used, though some records are organized by barony within the county.
Many record groups are organized by county and then by jurisdictions within that county. Ireland has 32 historical counties; six in Northern Ireland and 26 in the Republic of Ireland.
From the July/August 2015 Family Tree Magazine