Mather worked primarily in the lumber industry. Starting his working life in Scotland as a millwright and machinist before immigrating to Canada in 1857 to manage Gilmour’s lumber operations on the Gatineau and Ottawa rivers. Later, he became a central figure in the development of northwest Ontario, being involved in almost every industry of importance in the region. He was also a director of the Bank of Ottawa and owner of the Manitoba Free Press.
Mather built “Munross” at 453 Laurier Ave. E. where he lived for 30 years between 1877 and his death in 1907. The house was likely built by his brother James, a leading Ottawa architect and sat on a beautiful property which won the Governor General’s garden competition several times. Mather loved flowers, giving flowers to charitable organizations and instituting the John Mather prize in local floral competitions. The house was renovated in 1928 by the architectural firm of Noffke, Morin and Sylvester for businessman J. Ambrose O’Brien in the style of a Tudor Revival mansion, as seen today.
In the 1870s, Mather was a business partner of Donald Smith (later Lord Strathcona) and George Stephens in the Lake of the Woods Milling Company. Although he never entered public life, the Ottawa Journal described him as a valued friend of Sir John A. Macdonald and an intimate friend of Alexander Mackenzie, Canada’s second prime minister. He was married for 66 years and had four children.
In the early 1940s, with all five sons in the service, O’Brien leased the house to the Department of National Defence, which used it as a residence for the Women’s Royal Canadian Navy Service (WRENS). The house’s 13 bedrooms, seven full bathrooms, and seven fireplaces made it ideal for housing the WRENS. It now houses the Cordon Bleu Cooking School.
Munross’s mirror-image twin is Laurier House that James Mather is also believed to have designed. The two houses were built within two years of one another.
 The bank existed from 1874 to 1919 when it was taken over by the Bank of Nova Scotia.have designed. The two houses were built within two years of one another.
 Smith and Stephens were the main sponsors of the Canadian Pacific Railway.
 Ottawa Journal, 11 June 1907, p 8.