George Stephen was one of the leading members of the business communities of Montreal and the British Empire. Born in Dufftown, Banffshire, Scotland in 1829, he was the son of William Stephen and Elspet Smith. After a brief apprenticeship in London, he emigrated to Montreal in 1850 to join his family, who had emigrated several years earlier. He joined the woolen importing firm begun by his cousin, William Stephen, and formed his own company, George Stephen and Company in 1866.

Stephen rapidly made his mark in Montreal. His involvement in the woollen trade led him to become the major shareholder in a number of companies. In the 1860s he branched into railways, taking a lead position in the Montreal Rolling Stock Company. Elected a director of the Bank of Montreal in 1871, he became vice-president in 1873 and was made president in 1876. There he exercised a major influence over the Montreal business community and the Canadian economy. He became acquainted with Sir John Alexander Macdonald, Conservative Prime Minister, and became an unofficial advisor to Macdonald and his government.

In 1873 he became involved in a railway venture with his cousin, Donald Alexander Smith, James Joseph Hill and Norman Kittson to complete the St. Paul, Minneapolis and Manitoba Railway from St. Paul to Winnipeg. The railway became one of the most profitable in North America and made the fortunes of each of the partners. In 1880, Macdonald encouraged Stephen to tackle the task of building the Canadian Pacific Railway from Montreal to British Columbia. He became the founding president in 1881 and was largely responsible for financing the railway. He left the presidency in 1888. He was made a baronet in 1886 and took the title, Sir George Stephen of Dufftown, Banffshire and Grand-Metis, Quebec. He was elevated to the peerage in 1891 and became Lord Mount Stephen of Mount Stephen, British Columbia and Brocket Hall, Hertfordshire. He was the first Canadian to be made a peer. In 1905 he was appointed Knight Grand Cross of the Royal Victorian Order. In 1880 he built a magnificent mansion on Drummond Street in Montreal. Designed by William Tutin Thomas, it remains one of the most opulent buildings in Montreal, today serving as the Mount Stephen Club. A pioneer of the development of the sport fishery in Quebec, Stephen fished the salmon rivers of eastern Quebec from the 1870s onwards. In 1880 he built a fishing camp at La Fourche, Causapscal, at the confluence of the Matapedia and the Cascapedia rivers. His fishing lodge, now known as "Matamajaw" is a museum open to the public. In 1886 he acquired several properties at Grand-Metis. His fishing camp, which he called Estevan Lodge, was completed in 1887. In 1890 Stephen retired to England, establishing residences at 25 St. James's Place and later 17 Carlton House Terrace in London and at Brocket Hall in Hertfordshire. Married to Charlotte Kane in 1853, they had no children but adopted Alice Brook as a girl. She married Sir Stafford Northcote, who was Governor of Bombay and the Governor-General of Australia from 1904 to 1908. Lady Mount Stephen was presented to Queen Victoria in 1887. The Queen and other members of the Royal Family, the Duchess of Albany, the Prince and Princess of Wales, the Duke and Duchess of Connaught, and the Duchess of Teck were their guests at Brocket. An avid fisherman, Lady Mount Stephen fished with her husband in Canada and the rivers of Scotland. She apparently introduced the canoe to Scotland during one of her stays there. She died in 1896. In 1897 Lord Mount Stephen married Gian Tufnell, who had been Lady-in-waiting to Princess Mary Adelaide, Duchess of Teck, the mother of Queen Mary. She was a lifelong friend and confidant of Queen Mary and she and Lord Mount Stephen regularly entertained the Queen at Brocket Hall. She bequeathed her collection of jewels and her diamond tiara to her. Stephen remained active in imperial affairs and in the management of his investments in Canada, the United States and South America. He also became a generous philanthropist. In 1887 he and Donald Smith donated $500,000 each for the construction of the Royal Victoria Hospital in Montreal. In England, he continued his generosity to hospitals, donating $5 million to the King Edward's Hospital Fund during his lifetime. He left the residue of his estate of more than $4 million to the fund. He died at Brocket Hall on 27 November, 1921.