Thomas Ritchie was born on 5 July, probably in 1843 or 1844, at Downpatrick in County Down, Ireland, the son of John Ritchie, a farmer, and his wife Eliza McMurray. He went to a church society school and entered a private college. In 1863, lured by an older cousin's tales, he sold his horse for £25, pocketed the gift of a further £50 from his father, and sailed for New Zealand. He intended to go into business in Canterbury with his cousin, but on a cattle-buying trip to the Chatham Islands in February 1864 he changed his mind and leased 80 acres at Wairua, on the northern coast of Chatham Island, from Ngati Tama chief Heremaia Katene Te Raki. This was the beginning of the first sheep run on the Chathams and of Ritchie's 59-year residence there.
At first Tom Ritchie lived under the protection and guidance of Ngati Tama as 'Katene's Pakeha'. A number of Maori and Moriori worked as stockmen on his run. He employed as head stockman the disabled Hapurona Pawa, a local hero who had saved a number of people from drowning.
Ritchie was an innovative farmer, who built the island's first wool press. The discarded mechanical contraptions which littered his farm – there was no one to fix them if they broke down – were testimony to his search for modernity, and his restless, enquiring nature. In 1876 he imported a Clydesdale stallion and operated the first plough on the island. He loved horses and owned a large number of them. In 1873 he founded and became the first president of the Chatham Island Jockey Club. He entered his horses in the Chatham Island Cup until his retirement from racing in 1884.
From the beginning of his life on the islands Ritchie was also involved in the shipping business. He traded from a store at Owenga, and in 1868 Maori who wished to return home to Taranaki were carried in the Collingwood, a ship Ritchie chartered. In return for this service he gained the lease of large tracts of land. By 1866 he owned nearly 23,000 acres from Owenga to Te Awapatiki, and after 1868 leased a further 10,000 acres from Kaingaroa to Te Awapatiki. He later leased another large area south of Waitangi. He and his brother, Robert, eventually ran some 16,000 sheep on 55,000 acres – about a third of the total land area of Chatham Island.
The treacherous Chathams waters were the graveyard of many ships, and like other islanders Ritchie was in the salvage business. In 1877 he used the hulk of the 128-ton schooner Agnes, which had been wrecked in Waitangi harbour in 1876, to build the brigantine Island Lily. This traded to Australia and Fiji before being wrecked again at Te Raki in 1885.
Ritchie had employed some of the followers of Te Kooti, who were imprisoned with their leader at Waitangi on Chatham Island in 1866. When he discovered that an escape was being planned he warned the local administrator, but was ignored. When Te Kooti and the other prisoners escaped on 4 July 1868 Ritchie and a party of citizens made an epic ride through the night to Waitangi from Kaingaroa, unsure whether the island was in a state of war. In fact the escape was effected with only two fatalities.
The teachings of Te Whiti-o-Rongomai were influential among the Taranaki Maori left on the island after the exodus of 1868, and resulted in growing Maori assertiveness and the refusal to sign documents or sell land. When in 1872 it was rumoured that the followers of Te Whiti planned to massacre all Pakeha on the island the frightened citizens barricaded themselves in Lake House, the large house Ritchie had built on the shores of Lake Te Wapu at Kaingaroa. After a week in which the only invader was a pig, the settlers dispersed, and a subsequent military inquiry concluded that the threat had been remote.
On 5 February 1892 in Adelaide, South Australia, Ritchie married Mary Dobbs. In the rural depression of the 1890s he lost his run, and for a time is said to have lived on the charity of his Maori friends. In his last years on the Chathams he lived near Waitangi in a house on the beach at Te One where his son John farmed. The diaries he kept as an old man show that he turned increasingly to religion, while a poem he wrote, 'Our Chatham Island home', shows his intense emotional attachment to the island. In 1923 the Ritchie family left the Chathams. Thereafter Thomas lived in New Plymouth, where he died, aged 90, on 25 May 1934, survived by his wife and five children.
Thomas Ritchie had been in many ways a typical enterprising, courageous young single settler. What marks him out is the way he lived with the culture of his adopted home rather than seeking to dominate it, and the warmth and ease with which he crossed the barriers of race and class.
Ritchie was interested in the Moriori past in an amateur way, recording scraps of information and, on Moriori directions, taking from its hiding place at Tupuangi a unique sacred Moriori carving. It occupied a high place in Ritchie's affections, and is now in the Auckland War Memorial Museum. His papers reveal the keen interest he took in Maori and Moriori affairs. When he left Chatham Island Ritchie kept a remarkable series of letters (now in the Canterbury Public Library) from Maori and Moriori, which open a unique window on race relations in the nineteenth century.