The townland is a land division that is unique to Ireland. Townlands are entities in their own right and are not subdivisions of counties, baronies or parishes. Therefore, while most townlands will be found in their entirety within these larger land divisions, a proportion will be divided between two or more of them.

The townland system has been in existence for hundreds of years and continues to be important for local identity, especially in rural areas. The first thing to note about townlands is that they do not necessarily contain urban settlements. The word has its origins in the Old English word ‘tun’, meaning farmstead or settlement. By the early nineteenth century ‘townland’ had become a general term for a number of local words for small units of land. For instance, in Cavan the term used was ‘poll’, while in Fermanagh and Monaghan it was ‘tate’, with ‘ballyboe’ used across much of the rest of Ulster.

Across Ireland as a whole there are over 60,000 townlands, of which some 16,000 are in Ulster. Their average size is approximately 300–350 acres, though this varies from 172 acres in County Monaghan to 457 acres in County Down. Generally speaking, the acreage of a townland depends on the quality of the land, so that in upland areas townlands will be much larger, occasionally extending to several thousand acres. Conversely, in low-lying areas townlands may be less than 100 acres. The smallest townland in Ulster is Old Church Yard in the parish of Termonmaguirk, which extends to just over half of one acre. As its name suggests, it is an old graveyard, in fact the site of the medieval parish church.

Townlands are important for genealogists for a number of reasons. They were crucial location identifiers for individuals and families across Ulster for centuries (and still are in many rural areas, especially in the Republic of Ireland). In church registers, newspaper advertisements, and gravestone inscriptions, to name a few, the address given for a particular individual or family will usually be the townland of residence. Landed estates were composed of blocks of townlands and farms were the subdivisions of those townlands (unless the townland comprised a single farm).

The meanings of townland names reflect many different things, including local geography, family names, animals, plants and folklore. ‘Bally’ is the most frequently met with prefix for a townland name and can be translated as ‘place’ or even simply as ‘townland’. Other popular prefixes include Derry (oak wood), Kil/Kill (church), Knock (hill), Drum (ridge) and Gort (field).

A number of townlands include an attached surname. Clady (known in earlier times as Altaclady) in Ardstraw parish, County Tyrone, is a good example of this. Originally a single unit of land, it is now five townlands, each with a surname attached: Clady Blair, Clady Haliday, Clady Hood, Clady Johnston and Liscreevaghan or Clady Sproul. It seems likely that these names derived from families resident in each of these divisions of Clady.