Located 33 kms south of Canberra, Tharwa Bridge spanning the Murrumbidgee River at Tharwa village, refects the technical, commercial and social environments of Australia in the 1890s. It is the oldest bridge in Australian Capital Territory (ACT) and its four central spans are the oldest surviving samples in the service of the innovative timber truss designed by the Australian born engineer Percy Allan. Allan utilised test data on Australian hardwood timbers published in 1893 by Professor Warren of Sydney University which enabled efficient use of the these timbers in the building of major bridges. Over 100 Allan truss bridges were built in the 35 years following the opening of the Tharwa Bridge in 1895.
In 1936 the original timber piers were replaced and new approach sections were built in 1945. In 1994 restoration work was carried out on the trusses in sympathy with Allanâ€™s original drawings.
Construction of the bridge in 1894/95 followed forty years of political pressure – over that time agricultural and grazing development had expanded in the region. The NSW Government railway had been extended to nearby Michelago in 1887 and there was a pressing need to move sheep and wool across the Murrumbidgee River and provide access to the south including the Kiandra goldfields.
In 1980 the National Trust of Australia (ACT) recognised the heritage significance of the bridge, and it was entered on the Register of the National Estate in 1983. On the centenary of the opening of the bridge in 1995, the Institution of Engineers, Australia – now Engineers Australia – recognised the engineering significance of the structure by awarding it a National Engineering Marker. The plaque was unveiled by the ACT Chief Minister Kate Carnell during the centenary celebrations on 27th March 1995.
Following much community agitation over plans to replace the bridge with a modern structure, the ACT Government decided in 2009 to rebuild the bridge.