James Adams Mathewson was born on September 1, 1822, in Strabane, Tyrone, Northern Ireland.

He was a businessman. He immigrated to Montreal with his parents in 1834. In 1848, he became his father's partner in Samuel Mathewson & Son, a retail and wholesale firm specializing in tea, coffee, spices, sugar, and groceries. When his father died in 1854, James Adams joined forces with his brother-in-law Hugh Mathewson (1813-1877) under the business name J. A. and H. Mathewson. Together, they moved away from the retail business and began to operate as importers and wholesalers. In 1868, James Adams Mathewson ended his partnership with Hugh Mathewson and ran the family business alone for many years. His three sons (William Black, Samuel James, and James Adams, Jr.) were gradually introduced to the business and by 1884 were formally involved in the management of J.A. Mathewson and Company.

In 1847, he married Amelia Seabury Black (1826–1900). He died on April 3, 1905, in Montreal, Quebec.

Montreal and Ottawa investment banker F. Stanton Mathewson was born in Winnipeg and graduated from Trinity College School in Port Hope, Ontario. He became chairman of the Montreal Stock Exchange in 1930. He also served in the military during the two world wars. In 1914, he headed overseas with the 13th Battalion of Canada (the Black Watch) where, as a colonel, he was second in command of his regiment; he returned to Canada in 1916, wounded, with a D.S.O. for exceptional gallantry. In 1940, he again enlisted and was in command of troops in training in England until he was invalided home in 1942.