George Thornton was baptised in Beverley, Yorkshire, on 10 October 1828, one of the 11 children of William Thornton (b. circa 1795 at Cowick, Yorkshire), a railway contractor, and his wife Mary (b. circa 1799 at Beverley).
In his youth his family travelled the country following his father’s occupation, with his younger siblings born in Norfolk, Northamptonshire, Yorkshire and Essex. In 1851, George Thornton married Jane Kirkness (b. 1830 in Cowick, Yorkshire) in Goole, Yorkshire, and in 1853 they immigrated to Australia, living near Melbourne, in Hawthorn and Collingwood.
In 1862 Thornton and Jane moved to New Zealand, and on 17 November 1863 Samuel Bealey appointed him Assistant Provincial Engineer for Canterbury, under Edward Dobson, at a salary of £750 per annum. Thornton prepared the plans for the Godley Head lighthouse, letting the contract on 21 March 1864.
Thornton was elected Associate Member of the Institution of Civil Engineers (ICE) in 1866. In April 1867 he reported on erosion at Timaru, and on 1 June 1867 he was gazetted Engineer and Inspector of Roads for Canterbury. He was appointed Acting Provincial Engineer on 1 June 1868, after Dobson left for Australia following difficulties with the Lyttelton Harbour works, and Railway Engineer for Canterbury in February 1869.
In May 1869, Thornton produced a report on Lyttelton tunnel that was highly critical of Dobson. He let the contract for the construction of the Rakaia railway bridge, the longest bridge in the country, to William White on 7 October 1869, and on 29 August 1871 signed the contract for its conversion to a road/rail bridge. In this contract W B Bray acted for the General Government, which decided to take over all railway building. In 1872, he reported on the partial failure of the Opihi Bridge, where the piles had not been driven deep enough.
On 28 January 1874, he became Provincial Engineer for Canterbury, and in 1875 he and others were censured by a commission of enquiry for wasting money on the Rakaia Bridge. The Provinces were abolished in 1876, and he was compensated with £708/12/6 for his consequent loss of office. Unlike many other engineers he did not join the Public Works Department, and instead went into private practice in Christchurch, later in partnership with W J Bull.
In 1878 he was elected a Member of the ICE, and in 1879 he and Bull surveyed a railway route between Oamaru and Naseby for a local syndicate, and reported on stock-watering water-races for Ashburton County Council, as later built by William Baxter between 1879 and 1905. He contributed a paper on blasting in the Lyttelton Harbour works to the ICE (vol. LVI, p. 275).
His wife Jane died on 2 July 1901. Thornton continued as a consulting engineer until 1913, dying of cerebral apoplexy at Sumner on 19 July 1914.
They had three children: Clara Constance, later Sweet (1855–1939); Edwin Seymour (1857–1871); and Everard Kirkness (1862–1937). Thornton, his wife, Clara and Everard are buried in adjacent plots in Linwood Cemetery, Christchurch.
