Donald senior had been encouraged to migrate to New South Wales by Governor Macquarie who wished him to assist with government building works.

He worked on stone railway bridges at The Great Zig Zag and Marrangaroo, and married Marion Wiles, daughter of one of the construction foremen.

After the failure of the deep lead gold boom of the 1870s George returned to the Lithgow valley and established a construction business with Thomas Crowe.

[1][5] Located approximately 163 kilometres (101 mi) from Central station, the single-track Marrangaroo railway viaduct comprises eight 9-metre (30 ft) sandstone arches,[6] filled with stone rubble.

The viaduct was designed by John Whitton, Chief Engineer of Railways, and built by George McGarvie Donald with convict labour.

[1] The underbridge at Marrangaroo is significant as one of a small series of early stone arch railway viaducts built in New South Wales in the mid-to-late nineteenth century.

The bridge has historical significance, largely due to its contribution to the early and continuing development of railway infrastructure and services in western NSW in the late nineteenth century and early twentieth century, and also as an example of the use of local sandstone during a period of economic restraint but rapid expansion of railway services during which Whitton was required to use local materials as far as possible in bridge construction.