Blackrock Bridge, Lislap West, Omagh, Co Tyrone

Blackrock Bridge is a substantial early twentieth-century steel railway bridge carrying the former Great Northern Railway over the Strule River. It represents an important technological progression in structural engineering, necessitated by the introduction of improved rolling stock, and the railway itself was instrumental in the industrial development of the district, facilitating trade and improving communication links.

The bridge is a skewed single-span steel deck railway bridge, aligned north to south. It comprises a latticed steel trough supported centrally on a substantial lozenge-shaped tapered pier formed into a V at either side and faced in dressed stone. A stone string course runs above the mid level, above which the stone is rock-faced. The rails are held in place by a series of profiled sections riveted to the deck, which further support a steel rail parapet. The bridge terminates with rock-faced stone piers located on the steep banks at either side. It is situated in a rural setting with grassed banks and open pasture on either side.

The bridge first appears, captioned as 'Blackrock Bridge', on the second edition Ordnance Survey map of 1852, at which point the railway was captioned as the Londonderry & Enniskillen Railway. By the third edition map of 1905–6, this had become the Great Northern Railway (Ireland). The construction of the present bridge, along with other wooden bridges on the line, appears to have taken place in 1910–11.

The Londonderry & Enniskillen Railway Company was incorporated in 1845 and authorised to construct a single-track line extending southwards from Londonderry. Work began shortly after and by April 1847 the line had reached Strabane. Construction costs were relatively low, at approximately £10,000 per mile. However, due to the shortness of this initial section, storm damage, and competition from the Strabane Canal and Foyle Navigation, the first section was not a great commercial success. It was only with the construction of the line to Omagh (reached in 1852), Fintona (1853), and Enniskillen (1854) that the full benefits of the railway became apparent. The new rail communication brought important commercial advantages to the towns it served and indirectly to the agricultural lands along the valleys of the Foyle and its tributaries, as well as to flanking upland areas. Omagh and Strabane emerged as major market centres from which goods could be conveyed northwards to the port of Londonderry.

The Londonderry and Enniskillen Railway was leased to the Dundalk & Enniskillen Railway Company in 1860, which became the Irish North Western Railway Company. The Irish North Western Railway was absorbed by the Northern Railway Company on 1 January 1876, and this in turn merged with the Ulster Railway Company on 1 April 1876 to form the Great Northern Railway Company (Ireland). Several original bridges on the line, including earlier cast-iron girder trellis bridges that had themselves replaced the original timber bridges erected around 1850, were replaced in 1910–11 with enclosed troughs of riveted iron sheets supported on massive steel girders. Although Blackrock Bridge is situated along the Newtownstewart to Omagh stretch of the line rather than the Newtownstewart to Strabane stretch, comparison indicates that this bridge too may have been reconstructed around this period.

During the post-war period, railways faced increasing competition from road transport. In 1953 the Great Northern Railway ceased to exist as a separate and independent company; the entire system was acquired jointly by the Governments of Northern Ireland and the Republic of Ireland and subsequently operated by a Board consisting of representatives of both governments. In 1958 the greatly diminished portion of the former Great Northern system within Northern Ireland passed under the absolute control of the Ulster Transport Authority. A period of contraction followed in which many lines deemed unremunerative were closed down.