Railway Construction
Background
The first basic tramways in Ireland were built in the 18th century for hauling coal and similar materials by horsepower. The first steam locomotives were invented in the early decades of the 19th century. Â The first railway in the modern sense, was promoted in 1821 to bring coal from Durham to the coast. Â In 1825, this was opened as the Stockport and Darlington Railway. Â It was both a passenger and freight railway.
The first railway authorised in Ireland was Limerick and Waterford Railway, which contemplated steam locomotives. Â Despite Board of Public Works support, the finance required was not raised and the railway did not proceed at that time.
Ireland’s first railway was Dublin and Kingstown (Dun Laoghaire) Railway, which opened in 1834.  The initial purpose was to improve communications between the City and Kingstown Harbour due to difficulties of navigation in Dublin Bay. The Dublin and Kingstown Railway Act was passed in 1831.  The Board of Works assisted the project with a substantial loan. In practice, the route was quickly used as a passenger route.
Early Projects
Many lines were proposed and promoted, but most failed to achieve the requisite finance in the 1830s. Â A financial crisis in 1836 caused a slowdown in trade and commerce.
Commissioners were appointed in 1836 to enquire into a general system of railways for Ireland. They were tasked with planning of a system of railways. Their report, when published in 1838 was largely ignored.  They concluded that railways in Ireland were not viable and proposed a number of cross-country lines with branches.  It did not propose a direct line to Belfast nor to the West Coast.  It expressed the view that public monies would be required.
The only railway promoted in the initial mania of the 1830s, which was actually constructed was the Belfast to Lisburn line. The Ulster Railway Act was passed in 1836. It was completed in 1839.
Southern Trunk Lines
By 1850, most of the key trunk national routes had been established. Â Many of the routes that have survived to this day, date from that era. Â The next 30 years saw an expansion of railways into most parts of Ireland. Â Branch lines were promoted through most counties in Ireland.
The Great Southern and Western Railway planned a trunk line to the south and west to link Dublin, Limerick and Cork. Â The Great Southern and Western Railway Act passed parliament in 1844. With a mainline to Cork and a branch line to Carlow. Â Â Services commenced in 1848.
The Waterford and Limerick Railway was authorised in July 1845 reviving the original parliamentary backing in 1826. Â It crossed the GSWR route at Limerick junction, connecting Limerick and Tipperary to Dublin in 1848.
The Waterford and Limerick Railway continued construction in the 1850 and reached Waterford (from Limerick junction in 1854).  In 1846, the Killarney Junction Railway was authorised to build a line from Mallow to Killarney, which was a popular tourist route.
The English Great Western Railway through a subsidiary the South Western Railway, started to promote a port south of Wexford to link with West Wales in order to attract lucrative traffic across the Irish Sea.
Northern Trunk Lines
Companies vied with each other to obtain parliamentary approval authorising construction of routes. In the case of the Dublin to Belfast route, rival groups promoted an inland and coastal route. A third route,  to Drogheda route was mandated by act in 1836 and competed in 1844.
The Dublin and Belfast Junction Railway was formed to build a line between Drogheda and Portadown with a branch from Drogheda to Navan. Â This opened in 1850.
The Londonderry and Enniskillen Railway promoted a link via Strabane and Omagh.  The  Belfast and County Down Railway was incorporated by 1846 Act to build a line from Belfast.
The line between Dublin and Belfast was finally completed in the 1850s. Two major bridges were required at Newry and Drogheda; the Craigmore and Boyne viaducts. By 1853, trains ran the whole way from Belfast to Dublin.
Western Trunk Lines
The Midland Great Western Railway proposed a line to Galway through Mullingar and Athlone. The directors proposed an exchange of shares with the Royal Canal Company to facilitate the construction of the railway along the canal.
The Midland Great Western Act 1845 authorised construction of a line from Dublin to Mullingar and Longford. A line to Galway was authorised in 1847 as well as a line from Portarlington to Tullamore. The railway was complete by 1848.
The Dublin to Galway line was completed in August 1851 by the Midland Great Western Railway.  The Great Southern and Western Railway line to Tullamore opened in 1854. The Midland Great Western promoted its line from Mullingar to Longford and Cavan. The Sligo Extension Act 1857 allowed raising of additional monies to complete the 58 miles to Sligo.
The GSWR
The Great Southern and Western Railway became Ireland’s largest railway company. Â The Great Southern and Western Railway opened a direct line from Limerick to the north towards Sligo partly by acquiring lines being constructed by other operators. Â This alternative route remains in existence.
The Great Northern and Western Railway was authorised in 1857 to build lines connecting Athlone to Castlebar, Westport and Ballina. These opened in 1866, Westport and Ballina 1873. An 1857 Act authorise the GSWR to completed its line to Athlone.It was not permitted to cross the Shannon.
In effect the Great Southern and Western Railway dominated a line from Dublin to Athlone and down the  Shannon to the south, while the Midland Great Railway dominated to the north.
North West
The Sligo, Leitrim and Northern Counties Railway was built to link Enniskillen and Sligo via Manorhamilton. The line opened from Enniskillen to Belcoo in 1879, reaching Manorhamilton in 1880.
Two branch lines that are constructed from the Londonderry and Enniskillen line. The Finn Valley Railway ran from Strabane to Stranorlar opening in 1863.  The other was a branch  running from Bundoran junction eight miles north of Enniskillen to Bundoran. This was built by the Enniskillen, Bundoran and Sligo Railway company.
Dublin and South East
The Dublin, Dundrum and Rathfarnham Railway was incorporated to build the Harcourt Street line being a direct route to Bray from Dublin through Dundrum, largely the  line of the present Luas.
The original Kingstown railway had been extended to Dalkey and with a planned extension to Bray. Dublin and Kingstown Railway had obtained powers to extend the line down to coast to  Bray and a further Act allowed it to sell their Bray line to the Dublin, Wicklow and Wexford Railway by 1851.
The name of the company was changed to the Dublin and Wicklow Railway which then merged with the Dublin renamed Dublin, Dundrum and Rathfarnham Railway on the amalgamation of the company.
The second of two lines to Bray were opened in July 1854 via Harcourt Street and Dun Laoghaire. Later that year, the line to Wicklow was opened.
The company became Dublin, Wicklow and Wexford Railway reaching Enniscorthy in 1863. The Dublin, Wicklow and Wexford Railway opened its new route to Wexford in 1870 authorised by act of Parliament in 1868.
Northern Branches
The core of the Ulster railways were laid down in the decade commencing 1840. Â The Ulster Railway constructed the first section of its line to Lisburn in 1839. An extension was made south by 1841 the entire line was constructed to Portadown. The 1845 Act permitted construction of the line to Armagh.
Having constructed the railway to Armagh by 1848, the Ulster Railway developed its plan to head west. An extension to Monaghan was opened in 1858 and Clones in 1863.  The line was continued to Cavan and the Clones and Cavan extension railway was established under the D& E .The Ulster Railway, Dublin and Belfast Junction Railway and D & E contributed to the cost of the line. At Cavan, the line made a junction with the Midland Great Western line which had reached the town by 1856.
The Belfast and Northern Counties Railway had been incorporated as Belfast and Ballymena Railway in 1845.  It operated services to Carrickfergus, Ballymena and Randalstown. The Londonderry and Coleraine Railway was promoted in 1845.  The line eventually reached Coleraine by 1853.  The gap between this railway and Ballymena was built by the Ballymena, Ballymoney, Coleraine and Portrush Junction Railway. In 1860, the River Bann was bridged connecting the railways lines allowing for through  running from Belfast to Derry City.
The Belfast and Northern Counties Railways absorbed other railways taking over the London and Coleraine Railway and the Ballymena, Ballymoney, Coleraine and Portrush Junction Railway. It  absorbed the Carrickfergus and Larne railway incorporated to build a line from Carrickfergus to Larne Harbour.  The Belfast and Northern Counties Railway absorbed the Derry Central Railway which diverged from the Cookstown branch to the area west of the Bann  to meet the main line three miles from Coleraine.
The Dundalk, Newry & Greenore Railway had two lines one from Dundalk to Greenore and one from Greenore to Newry. It was promoted by the London and North Western Railway and was intended to capture traffic across the Irish Sea. Greenore was promoted as a port but never usurped Holyhead to Dublin or Belfast to Fleetwood.
The GNR
The Ulster Railway also promote the building of the line from Portadown to Dungannon and Omagh. Â At Omagh, the line made a junction with the Londonderry and Enniskillen line from Derry and provided a second route through Belfast to Derry.The Dungannon and Omagh Railway company was backed by Ulster Railway. Â It took a lease of the line.
In 1875, the D&D and Dublin and Belfast Junction Railway merged to form Northern Railways. The D & E leased the London and Enniskillen line and changed its name to Irish North Western Railway.
It ultimately merged the Northern Railways in 1876 with the Ulster Railway to form the Great Northern Railway. The Newry and Armagh Railway also joined and became part in 1879.