[1] Whitton, a successful railway engineer from England, chose one of the famous I. K. Brunel's timber bridge viaducts built in Cornwall during the 1850s.

The model chosen was the St Germans Viaduct composed of composite deck Queen post trusses, the bottom chords were large iron rods.

[1] The final section to Wallangarra, 1888, was mostly easier over plateau country but the crossing of Tenterfield Creek required a large bridge and a timber Queen post truss viaduct was built there also, the fourth between Glen Innes and the Queensland border.

[1] Only two other such timber viaducts were built in this period, on the Bombala railway line over Ingalara Creek and the Bredbo River, see separate inventories.

[1] Former railways chief David Hill called the old Great Northern line that first linked Sydney and Brisbane the most important stretch of heritage track in the country.

The NSW line came north from Tenterfield in 1888, but because the two systems used different track gauges, passengers had to change trains at Wallangarra's unique railway station.

The timber Queen post deck viaduct was a significant structure in place of the expensive iron lattice bridges preferred by John Whitton.

[1] The Sunnyside rail bridge over Tenterfield Creek was listed on the New South Wales State Heritage Register on 2 April 1999 having satisfied the following criteria.

This item is assessed as historically significant due to its association with the early expansion of the NSW railways to colonial borders during John Whitton's tenure as Engineer-in-Chief.

[1] The place is important in demonstrating aesthetic characteristics and/or a high degree of creative or technical achievement in New South Wales.

The timber Queen post deck viaduct was a significant structure in place of the expensive iron lattice bridges preferred by John Whitton.