Completed in 1898, Morpeth bridge is the oldest surviving example of an overhead braced Allan truss road bridge in service, and is one of three surviving overhead braced timber truss road bridges in NSW. Most of its engineering details are intact, and the bridge is in good condition.
Allan trusses were a major development which superseded the McDonald truss bridges which preceded them, and were an extremely successful design. Major innovations were made in the areas of maintenance, cost of construction, and the achievable span length. The bridge has a high degree of technical significance.
Timber truss bridges were important in the development of the road network in NSW. Before the construction of these bridges, river crossings were often treacherous, and an impediment to efficient transport. Through this, the expansion of rural NSW, particularly the mining and agricultural sectors, was facilitated.
The bridge has a historical association with Percy Allan, senior bridge designer at the Public Works Department, and is important to the history of Morpeth.
Morpeth Bridge is located in the Hunter region, which has 15 historic bridges each constructed before 1905, and it gains heritage significance from its proximity to the high concentration of other historic bridges in the area.
In 1998 there were 38 surviving Allan trusses in NSW of the 105 built, and 82 timber truss road bridges survive from the over 400 built.
Morpeth bridge is a representative example of overhead braced Allan timber truss road bridges, and is assessed as being Nationally significant, primarily on the basis of its technical and historical significance.