The Great Northern Railway (Ireland) (GNR(I) or GNRI) was an Irish gauge (1,600 mm (5 ft 3 in) railway company in Ireland. The Great Northern was formed in 1876 by a merger of the Irish North Western Railway (INW), Northern Railway of Ireland, and Ulster Railway. The Ulster Railway was the GNRI’s oldest constituent, having opened between Belfast and Lisburn in 1839 and extended in stages to reach Clones in 1863. The Northern Railway of Ireland was itself formed by a merger of the Dublin and Drogheda Railway (D&D) with the Dublin and the Belfast Junction Railway (D&BJct).
The Ulster, D&D and D&BJct railways together formed the main line between Dublin and Belfast, with the D&BJct completing the final section in 1852 to join the Ulster at Portadown. The GNRI’s other main lines were between Derry and Dundalk and between Omagh and Portadown. The Portadown, Dungannon and Omagh Junction Railway together with the Londonderry and Enniskillen Railway enabled GNRI trains between Derry and Belfast to compete with the Belfast and Northern Counties Railway, and both this and the Dundalk route gave connections between Derry and Dublin. These main lines supported the development of an extensive branch network serving the southwest half of Ulster and northern counties of Leinster. The GNRI became Ireland’s most prosperous railway company and second largest railway network.
In its early years the GNR closely imitated the image of its English namesake, adopting an apple green livery for its steam locomotives and a varnished teak finish for its passenger coaches. Later the company adopted its famous pale blue livery for locomotives (from 1932), with the frames and running gear picked out in scarlet. Passenger vehicles were painted brown, instead of varnished
A combination of the increasing road competition facing all railways and a change in patterns of economic activity caused by the partition of Ireland reduced the GNRI’s prosperity. The company modernised and reduced its costs by introducing modern diesel multiple units on an increasing number of services in the 1940s and 1950s and by making Dublin–Belfast expresses non-stop from 1948. In Dundalk at the GNR Works the railway engineers developed railbuses for use on sections of the rural network. Nevertheless, by the 1950s the GNRI had ceased to be profitable and in 1953 the company was jointly nationalised by the governments of Ireland and Northern Ireland. The two governments ran the railway jointly under a Great Northern Railway Board until 1958.
In May 1958 the decision by the Government of Northern Ireland to close many lines led to the GNRI Board being dissolved and the assets divided between the two territories. All lines in Northern Ireland were transferred to the (nationalised) Ulster Transport Authority (UTA) and all lines in the Republic of Ireland were transferred to Córas Iompair Éireann (CIÉ). CIE had been formed as a private company in 1945 but had been nationalised in 1950. In an attempt at fairness, all classes of locomotive and rolling stock were also divided equally between the transport operators of the two new owners. Most classes of GNRI locomotive had been built in small classes, so this division left both railways with an operational and maintenance difficulty of many different designs all in small numbers.
The Northern Ireland Government, which had a very anti-rail policy, rapidly closed most of the GNRI lines in Northern Ireland. Exceptions were the Belfast–Dundalk and Portadown–Derry main lines and the Newry–Warrenpoint and Lisburn–Antrim branches. It made the Lisburn–Antrim branch freight-only from 1960 and closed the Portadown–Derry and Newry–Warrenpoint lines to all traffic in 1965. The Republic of Ireland government tried briefly to maintain services on lines closed at the border by the Northern Ireland government, but this was impractical, and the Republic had to follow suit in closing most GNRI lines south of the border. Since 1960 the Drogheda–Navan branch has survived for freight traffic only.
Today, the GNR routes remaining consist of the main line from Dublin to Belfast, the Howth branch, electrified for Dublin commuter services since 1984, the Drogheda – Navan (Tara Mines) line, which carries only freight traffic associated with that mine, passenger traffic having ceased with the closure of the line beyond there to Oldcastle in 1963, and the Lisburn to Antrim branch, now mothballed but retained in operational order for the time being