The smallest official geographical division used in Ireland is the townland. Loosely related to the customary rural and agricultural divisions used in post-medieval Ireland - the 'ballybetagh' in the north-west, the 'cappel' lands and 'ploughlands' in the south-east, the ceathrú (quarter) in the west - townlands began to undergo standardisation from the seventeenth century. They retain a loose relationship with agricultural value and can therefore vary enormously in size, from a single acre or less to several thousand acres. There are more than 64,000 townlands in Ireland. The final standardisation was carried out by the Ordnance Survey in the 1830s, and the versions they chose (or imposed) are still in use today. Standardisation resulted in the loss of a large number of traditional names, later referred to as 'sub-denominational'.
Anything from five to thirty townlands may be grouped together to form a civil parish. These are a legacy of the Middle Ages, pre-dating the formation of counties and generally co-extensive with the parishes of the Established Church, the Church of Ireland. They are not to be confused with Catholic parishes, which are usually much larger. In turn, civil parishes are collected together in baronies. Originally related to the tribal divisions, the tuatha, of Celtic Ireland, these were multiplied and subdivided over the centuries up to their standardisation in the 1500s, so that the present names represent a mixture of Irish, Anglo-Norman and English influences. A number of baronies, from five in Co. Leitrim to twenty-two in Co. Cork, then go to make up the modern county. Baronies and civil parishes are no longer in use as administrative units.
These geographical units are the basis of the only two nineteenth-century
property surveys to cover the entire country. Because of the destruction of early 19th-century
census returns, the Tithe Applotment Books of c.1823-38 and Griffith's
Valuation, dating from 1847 to 1864, have acquired a somewhat unnatural