Following the Anglo Irish treaty, the exact border between the new dominion of the Irish Free State and the future Northern Ireland, if it chose to opt out, was to be decided by the Irish Boundary Commission. This did not announce its findings until 1925, when the line was again drawn around six of Ulster’s nine counties, with no change from the partition of 1920.
Electorally, voting in the six Northern Ireland counties of Ulster tends to follow religious or sectarian lines; noticeable religious demarcation does not exist in the South Ulster counties of Cavan and Monaghan in the Republic of Ireland. County Donegal is largely a Roman Catholic county, but with a large Protestant minority. Generally, Protestants in Donegal vote for the political party Fine Gael (“Family of the Irish”). However, religious sectarianism in politics has largely disappeared from the rest of the Republic of Ireland. This was illustrated when Erskine H. Childers, a Church of Ireland member and Teachta Dála (TD, a member of the lower house of the National Parliament) who had represented Monaghan, won election as President after having served as a long-term minister under Fianna Fáil Taoisigh Éamon de Valera, Seán Lemass and Jack Lynch.
The Orange Order freely organises in counties Donegal, Cavan and Monaghan, with several Orange parades taking place throughout County Donegal each year. The only major Orange Order march in the Republic of Ireland takes place every July in the village of Rossnowlagh, near Ballyshannon, in the south of County Donegal.
As of 2017, Northern Ireland has seven Roman Catholic members of parliament, all members of Sinn Féin (of a total of 18 from the whole of Northern Ireland) in the British House of Commons at Westminster; and the other three counties have one Protestant T.D. of the ten it has elected to Dáil Éireann, the Lower House of the Oireachtas, the parliament of the Republic of Ireland. At present (August 2007) County Donegal sends six T.D.’s to Dáil Éireann. The county is divided into two constituencies: Donegal North-East and Donegal South-West, each with three T.D.’s. County Cavan and County Monaghan form the one constituency called Cavan-Monaghan, which sends five T.D.’s to the Dáil (one of whom is a Protestant).
The historic Flag of Ulster served as the basis for the Ulster Banner (often referred to as the Flag of Northern Ireland), which was the flag of the Government of Northern Ireland until the proroguing of the Stormont parliament in 1973.
The biggest lake in the British Isles, Lough Neagh, lies in eastern Ulster. The province’s highest point, Slieve Donard (848 metres (2,782 ft)), stands in County Down. The most northerly point in Ireland, Malin Head, is in County Donegal, as are the sixth-highest (601 metres (1,972 ft)) sea cliffs in Europe, at Slieve League, and the province’s largest island, Arranmore. The most easterly point in Ireland is also in Ulster, in County Down, and the most westerly point in the UK is in County Fermanagh. The longest river in the British Isles, the Shannon, rises at the Shannon Pot in County Cavan with underground tributaries from County Fermanagh. Volcanic activity in eastern Ulster led to the formation of the Antrim Plateau and the Giant’s Causeway, one of Ireland’s three UNESCO World Heritage Sites. Ulster also has a significant drumlin belt. The geographical center of Ulster lies between the villages of Pomeroy and Carrickmore in County Tyrone. In terms of area, County Donegal is the largest county in all of Ulster.
The GDP of the province of Ulster is around €50 billion. Salary levels are the lowest on the island of Ireland.
The province’s main airport is Belfast International Airport (popularly called Aldergrove Airport), which is located at Aldergrove, 11.5 miles northwest of Belfast near Antrim. George Best Belfast City Airport (sometimes referred to as “the City Airport” or “the Harbour Airport”) is another, smaller airport which is located at Sydenham in Belfast. The City of Derry Airport is located at Eglinton, 13 kilometres (8 mi) east of the city of Derry. There is also Donegal Airport (Irish: Aerfort Dhún na nGall), popularly known as Carrickfinn Airport, which is located in The Rosses.
Railway lines are run by Northern Ireland Railways (NIR). Belfast to Bangor and Belfast to Lisburn are strategically the most important routes on the network with the greatest number of passengers and largest profit margins. The Belfast-Derry railway line connecting Londonderry railway station, via Coleraine, Ballymoney, Ballymena and Antrim, with Lanyon Place and Belfast Great Victoria Street is a noted scenic route. Belfast is also connected with Carrickfergus and Larne Harbour, Portadown, Newry and onwards, via the Enterprise service jointly operated by NIR and Iarnród Éireann, to Dublin Connolly.