from web site
While Lifford is the county town, Letterkenny is without a doubt the largest town in the county with a population of simply under 20,000. Letterkenny and the close-by city of Derry form the main financial axis of the northwest of Ireland. Certainly, what ended up being the City of Derry was officially part of County Donegal up until 1610.
Baronies and townlands [modify] There are 8 historical baronies in the county. While baronies continue to be formally specified systems, they stopped to have any administrative function following the City government Act 1898, and any changes to county borders after the mid-19th century are not reflected in their extent. Solution Can Be Seen Here of a barony in Donegal was in 1851, when the barony of Inishowen was divided into Inishowen East and Inishowen West.
With an area of 312,410 acres (1,264 km2), Kilmacrennan is also the largest barony in Ireland, being approximately equivalent in size to County Monaghan. The smallest barony is Inishowen West, at 77,149 acres (312. 21 km2). Townlands are the smallest formally specified geographical departments in Ireland. There are 2,787 townlands in Donegal, and an additional 47 historical town limits.
The smallest rural townlands in Donegal are simply 1 acre in size, most of which are either lough islands or overseas islets (Corragh Island, Bishop's Island, Juniper Island, O'Donnell's Island, and so on). The largest rural townland in Donegal is 6,053 acres (Tawnawully Mountains). The typical size of a townland in the county (excluding towns) is 438 acres.
There are two Gaeltacht districts in the west: The Rosses (Irish: Na Rosa), centred on the town of Dungloe (Irish: An Clochn Liath), and Gweedore (Irish: Gaoth Dobhair). Another Gaeltacht district is situated in the north-west: Cloughaneely (Irish: Cloich Chionnaola), centred on the town of Falcarragh (Irish: An Fl Carrach).
The main population centre of Inishowen, Ireland's largest peninsula, is Buncrana. In the east of the county lies the Finn Valley (centred on Ballybofey) and The Laggan district (not to be confused with the Lagan Valley in the south of County Antrim), which is centred on the town of Raphoe.