George Henry Moore, son of the landowner Thomas Moore and his wife, Catherine Currin, was born at Billown, Isle of Man, England, probably on 12 October 1812, and was baptised at Malew on 1 January 1813. About 1830 he emigrated to Tasmania with his friend Robert Quayle Kermode. Moore worked as a cadet on Mona Vale, the sheep run of William Kermode, Robert's father. On 9 July 1839 Moore married William Kermode's daughter, Anne, at Avoca, Tasmania. They had four children before they separated.
In the early 1850s Robert Kermode and Moore became interested in New Zealand runholding, and Moore arrived in Lyttelton in mid 1853 to investigate prospects. After prolonged searching he decided on parts of the Glenmark, Teviotdale, Motunau and Horsley Downs leases, just north of the Canterbury block, and in March 1854, on Kermode's behalf, purchased 40,000 acres for £17,000. On his return to Tasmania Moore entered into a partnership, Kermode and Company, with his son William, Robert Kermode and Dr John Lillie. Moore was to be manager; his senior partners put up the bulk of the capital. In three voyages of the William Hyde from Hobart between February and June 1855, Glenmark was stocked with about 6,000 Tasmanian merino sheep. Further purchases raised Glenmark's freehold to 60,000 acres. The partners also bought the leases of Wakanui, Rokeby and part of Longbeach, but these areas were nearly all sold by 1874. By 1864 the Glenmark flock had increased to 64,000.
In 1866 the partnership was reduced to Kermode and Moore, following the deaths of William Moore in 1865 and John Lillie in 1866. Moore, still manager, was empowered to buy a half-share, an indication of his rising status and resources. After Kermode's death in 1870 the properties had to be put up for auction. The February 1873 private run sale was the largest and most celebrated thus far in New Zealand history. Against stiff competition Moore purchased 38,935 acres of freehold, to which was attached 78,470 acres of leasehold. By 1882 Moore's property had easily the highest value in the colony, £362,780. At its peak Glenmark carried more than 90,000 sheep. To match this pastoral princedom Moore erected a mansion, designed by S. C. Farr and completed in 1888. One feature betrayed Moore's suspicious nature: there was no back door.
By this time Moore and Glenmark were established as New Zealand legends, and Moore's three-legged Manx brand as a symbol of colonial wealth. At its greatest extent the station covered about 150,000 acres, of which 81,000 were freehold. Moore made the initial discovery of moa bones on Glenmark in 1857, leading to Julius Haast's excavations and spectacular discoveries.
The Glenmark legends had a dark and even repugnant side. Moore was widely seen as a hard employer and a bad neighbour. Glenmark was for years Canterbury's scabbiest run, and its owner notorious as 'Scabby Moore'. In 1864 his fines for owning diseased sheep amounted to £2,400. Possibly Moore sought to discourage prospective purchasers of his leasehold land by keeping the run infected. In March 1860 Moore displayed conspicuous callousness towards an elderly swagger seeking shelter at Glenmark on a stormy night. Moore refused to let him stay and the swagger shot himself. When the police arrived to remove the body, Moore was unhelpful. In reporting the inquest, the Lyttelton Times excoriated Moore as a 'Mean, hard-hearted, barbarous, blasphemous man!' By the 1890s Glenmark was a prime target for opponents of land monopoly. Moore forestalled radical critics by selling off large areas, leaving only about 11,000 acres. He died at Christchurch on 7 July 1905. The probate value of his estate was £253,000.
Moore stands out in New Zealand pastoral history as a supremely successful runholder in terms of personal wealth. His skill, judgement and sense of timing were of a very high order. Yet without strong financial backing from partners and bank, the full achievement of Glenmark would have been impossible. His 1873 purchase was a bold decision, based on a mortgage of exceptional size to the Union Bank of Australia, which advanced Moore £90,000. The link between banking and large runholding in Canterbury was never more clearly demonstrated.
Moore's accumulation of wealth brought little enduring result. His only surviving and estranged son, William, had died young and childless. In February 1890 the Glenmark mansion was destroyed by fire. Moore sought to bind his daughter Annie to himself and to his estate, but she secretly married in 1900, when he had gone blind. On her death without children in 1914 the estate, approaching £1 million in value, was dispersed to numerous beneficiaries. Three contradictory symbols of Moore's Glenmark survive: the ruins of his mansion; the magnificent stables dating from 1881; and St Paul's Anglican Church, built on Glenmark in 1911 by his daughter, Annie Quayle Townend, in memory of her father.