The four provinces of modern Ireland – Ulster in the north, Leinster in the east, Munster in the south and Connacht in the west – form the largest units of geographical reference. The country was first divided into four provinces at the Synod of Kells in 1152 when the four Archdioceses of Armagh, Cashel, Tuam and Dublin were formed. In modern times the province is usually thought of as a cartographic and census division.
The thirty-two counties are the result of the imposition of the English shire system beginning in the twelfth century. Shires were instruments of local government administered by sheriffs. These officials had a great variety of functions including courts, collection of taxes and maintenance of highways. These functions were a reason for fixing definitive boundaries.
The basic territorial division of Celtic Ireland was the tuath (the territorial holdings of a clan). Historically there was a resemblance between the name of the territorial holding (barony) and the clan name (tuath). From the sixteenth century onward, the barony was widely used as an administrative, tax and regional entity within the county. The barony ceased to be a territorial division at the end of the nineteenth century. There were 331 baronies in Ireland.
In origin the parish is an ecclesiastical administrative division of great antiquity and indicates the area over which a clergyman exercised spiritual jurisdiction. With the extension of the Reformation to Ireland in the sixteenth century the parish ceased its prominence as a center of Catholic religious practice; it became a new civil territorial division and the parish of the Established Church. The Catholic Church, deprived of its buildings and land, had to adapt itself to a new parochial system. The poverty of the population and the restrictions on the priests ensured that the new parishes were large and unwieldy. Civil parishes frequently cross both barony and county boundaries. Catholic parishes, on the other hand, faithfully observe the county boundaries but often cross civil parish lines.
These are small areas of land such as family farms or group of farms. The townland is the smallest of the administrative divisions. The average townlands size is 350 acres – the smallest townland is a little over an acre while the largest is 7,000 acres.
Under the 1838 Poor Relief Act, the country was divided into districts or "unions" in which the local tax-payers were to be financially responsible for the care of the poor in their area. The unions were usually centered on a large market town and often crossed county boundaries. Beginning in 1851 each union was subdivided into dispensary districts.
These are units used to define local electoral areas. They are comprised of townland subdivisions of Poor Law Unions. The boundaries were drawn by a Poor Law Boundary Commission on the basis of creating equivalent "ratable value" and population in each division. DEDs were almost always contiguous but bore little relation to natural community boundaries. The 1901 and 1911 Irish censuses are recorded on the basis of the DED unit.
With the passage of the Civil Registration Act of 1863 each poor law union became a Superintendent Registrar's District for the registration of births, marriages and deaths; each dispensary district became a registrar's district. The boundaries of the new districts were coterminous with those of the poor law union and dispensary districts.
The Church of Ireland and the Roman Catholic Church are divided into large territories known as dioceses whose boundaries do not correspond to county boundaries nor to each other.
In 1858 a principal registry in Dublin and eleven district registries were established to prove wills and grant letters of administration. The boundaries of these probate districts follow either county or barony divisions.
The Irish experience has had a profound impact on Connecticut's past, and its narrative spans all periods of the state's history and touches every one of its eight counties and 169 towns.