The Dublin to Belfast Rail Link established a vital connection between the capitals of Northern Ireland and the Republic of Ireland. The line's most notable engineering feature was the 1,760-foot-long Boyne Bridge; it represented one of the earliest uses of calculated stresses, the first large-scale use of wrought iron latticed girders, and the first full scale test of continuous beams. Tests performed on the wrought iron columns and struts were published and provided invaluable information for engineers who would design similar structures in the future. 

Due to increased axel loads, weight, and speed restrictions imposed as early as 1885, the bridge was deficient to meet changing transportation requirements. By 1932, the original structure was removed and replaced with a steel bridge.  

The Craigmore Viaduct is another significant element of the rail link.  The graceful stone masonry viaduct has 15 semi-circular arches. It rises 137 feet above the Camlough River valley, making it the highest railway bridge in Ireland. 

Facts  

• The girders were produced using a lever punching press. This was the first engineering machine tool to be controlled by punched card. 
• Masonry piers were composed mainly of local limestone and founded on rock. 
• The bridge's three main spans ranged from 141 to 267 feet.