Robert Gilmour was born in Glasgow, Scotland, probably on 24 October 1831, the son of Robert Gilmour, a farmer, and his wife, Elizabeth Gemmell. Nothing is known of his life until he arrived in Auckland, New Zealand, in 1858. Soon afterwards he moved to Napier, where he took up farming and also contributed articles to the Hawke's Bay Herald. About 1862 Gilmour headed for the Southland goldfields. He lived at Nokomai and other mining centres before returning to farming at Hokonui, western Southland.
Farming life had little attraction for Gilmour, and, perhaps in 1864, he moved to Invercargill to work as a journalist on the Southland Times. On 4 April 1864 he married Margaret Carolan in Invercargill; they were to have one daughter. In 1869 Gilmour became part-proprietor of the Southland Times with James Walker Bain. Within a year he had left this partnership to join Bain's former partner, William Craig, in running the rival newspaper, the Southland News.
Margaret Gilmour died suddenly on 7 February 1873, and in 1874 Gilmour returned to Scotland to engage in commerce. On 27 July 1875 at Wishaw, Lanarkshire, he married Catherine Masterton Ritchie; they were to have seven sons and one daughter. Finding that Scotland's 'old fashioned prosaic ways and usages' were 'altogether irksome and distasteful', Gilmour returned with his wife and family to Invercargill in 1879. Almost immediately he bought John Chantrey Harris's share of the Southland Times and became managing director. He worked 16, sometimes 18, hours a day, and the paper prospered under his management.
Gilmour was still attracted to practical journalism. In 1886 he became revising editor, and in 1888 editor. In 1896 he bought out all other shareholders to become sole proprietor. The combination of editorial and management roles meant that Gilmour was well placed to withstand political pressure. When, in 1879, Sir George Grey's government refused to place advertisements with the Southland Times in retaliation to editorial criticism, he wrote that the newspaper depended 'not upon the corrupt favouritism of a corrupt Ministry, but upon the decision of a discriminating public.' This was not the only time his refusal to waver from a moral crusade drew criticism.
The firm principles which guided all Gilmour's writing were based on his deep-seated religious beliefs. His vigorous contributions to contemporary controversies were always grounded in his stern conception of justice and morality. He 'spoke strongly and wrote strongly against whatever he considered was contrary to truth and righteousness and likely to blunt the moral sense of the people.'
Gilmour was not a demonstrative man; he was a man of determined action who commanded respect and drew out what was best in others. He had a love of intellectual work, unflagging industry, keen powers of observation, strong common sense, and a severe taste in literature. His use of language was concise and trenchant; his presentation of the news honest and balanced.
As editor of the daily newspaper Gilmour was informed on all local body business. He was also an active member of the old Railway League, the Invercargill Chamber of Commerce, the Southland Agricultural and Pastoral Association and several minor bodies. He was associated with the Southland Hospital from its beginnings and was its last president while it was funded solely by donations. He strongly supported the building of what became the Invercargill Athenaeum. Proud of his Scottish heritage, Robert Gilmour was also a member and president of both the Caledonian Society of Southland and the Burns Club.
A devout Christian, Gilmour was a long-serving office bearer of St Paul's Presbyterian Church, and a member of its Literary and Musical Society, designed to attract young people. He still found time to pursue his interests in sport and reading, and for mental relaxation he practised speaking Latin with a close friend.
Ill health struck Gilmour in early 1901, but he continued to work full time until cancer was diagnosed in November. He wrote bravely of this illness in his columns. In February 1902 he took his sons Robert, David and Douglas into partnership. He died at his home in Invercargill on 24 April 1902. Catherine Gilmour died in Wellington on 1 February 1921.