parish of Termonmagurk, County Tyrone, at and the largest, at , was and is Fionnán (also called Finnaun) in the parish of Killanin, County Galway. In fact, the townland of Clonskeagh in the barony of Uppercross (abutting the main Clonskeagh townland in the barony of Dublin) was only although the area is now urbanised, so that the townlands are unused and their boundaries are uncertain. The ballyboe, a townland unit used in Ulster, was described in 1608 as containing 60 acres of arable land, meadow, and pasture. However, this was misleading, as the size of townlands under the Gaelic system varied depending upon their quality, situation and economic potential. This economic potential varied from the extent of land required to graze cattle to the land required to support several families. The highest density of townland units recorded in Ulster in 1609 corresponds to the areas with the highest land valuations in the 1860s. It seems that many moorland areas were not divided into townlands until fairly recently. These areas were "formerly shared as a common summer pasturage by the people of a whole parish or barony". Historical use Until the 19th century most townlands were owned by single landlords and occupied by multiple tenants. The cess, used to fund roadworks and other local expenses, was charged at the same rate on each townland in a barony, regardless of its size and productive capacity. Thus, occupiers in a small or poor townland suffered in comparison to those of larger or more fertile townlands. This was reformed by Griffith's Valuation. Irish Ordnance Survey and standardisation During the 19th century an extensive series of maps of Ireland was created by the Irish division of the Ordnance Survey for taxation purposes. These maps both documented and standardised the boundaries of the more than 60,000 townlands in Ireland. The process often involved dividing or amalgamating existing townlands, and defining townland boundaries in areas such as mountain or bog that had previously been outside the townland system. Slight adjustments are still made. There were 60,679 in 1911, compared to 60,462 townlands in 1901. Current use Townlands form the building blocks for higher-level administrative units such as parishes and district electoral divisions (in the Republic of Ireland) or wards (in Northern Ireland). Before 1972 townlands were included on all rural postal addresses throughout the island, but in that year the Royal Mail decided that the townland element