George W. Smith completed an apprenticeship as a civil engineer in 1858 and that same year came to the Cape Colony to become assistant engineer of the Cape Town to Wellington railway. In 1862 he was admitted to practice as a land surveyor in the Cape Colony. During preliminary surveys for the railway lines from Port Elizabeth to Uitenhage and Grahamstown that year he met the surveyor Robert Pinchin* and went into partnership with him. He practised as a surveyor in Port Elizabeth until work became scarce during the depression of 1868, when he went to Australia. After two years as an assistant in the surveyor-general's office in Melbourne he was employed on various railway and mining projects in India, Scotland, Canada, The United States, Spain and Italy. In 1876, in London, he married Rosetta Strang, with whom he had two sons and a daughter. In 1877-1878 he was involved in the development of the Millwood goldfields near Knysna. Eventually he returned to Port Elizabeth to resume his partnership with Pinchin in 1881. After Pinchin's death in 1889 the firm continued under the name Smith & Dewar. Following the discovery of gold on the Witwatersrand in 1886 Smith did some survey work there. He also worked as an architect and, among others, designed the Opera House (1892) and the Atheneum (1896) in Port Elizabeth.
In April 1886 Smith was elected a member of the Eastern Province Naturalists' Society. During the eighteen-eighties he published two articles in the Proceedings of the Mining Institute of Scotland, entitled "The diamond fields of South Africa" (1884) and "A mining tour through South Africa" (1887). Years later the presence of a series of salt pans north of Port Elizabeth convinced him that oil might be found there. He went to Galicia, Spain, to recruit oil drillers and started drilling at Zwartkops. However, all he found was a hot spring, where a spa was later built. He wrote up his discovery in the form of a paper, "Some notes concerning a deep bore at Zwartkops, near Port Elizabeth, and the resulting thermal chalybeate spring". The paper was published in the Report for 1912 of the South African Association for the Advancement of Science (pp. 119-127). By this time he was an associate member of the (British) Institution of Civil Engineers. In 1909 he presented Pinchin's original geological section of the colony, from Port Elizabeth northwards, to the Albany Museum.