Born as Donald Alexander Smith on 6th August 1820 in Forres, Moray in Scotland. He was apprenticed to the Hudson's Bay Company in 1838 and worked for many years at the fur trade in Labrador. He was chief commissioner for the Company from 1870-1874 and Governor from 1889 until his death in 1914.
Smith entered politics in 1870 as a Conservative member for Winnipeg in the new Manitoba legislature. Becoming a member for Selkirk in the Canadian House of Commons in 1871, he withdrew his support for the Conservative leader Sir John A Macdonald during the Pacific Railway Scandal of 1873. This contributed to the defeat of the Macdonald's ministry so when Macdonald returned to power Smith fell from favour. He promoted the St Paul, Minneapolis and Manitoba Railway. But because of Macdonald's antipathy he was not formally a member of the syndicate formed to build the Canadian Pacific Railway in 1880. But his financial support was vital and he was given the honour of driving the last spike at Craigellachie, British Columbia in 1885.
He became president of the Bank of Montreal in 1887 and honorary president in 1905. He was appointed High Commissioner for Canada in London in 1896 and granted a peerage in 1897. He raised Strathcona's Horse in 1900 to support Britain's war in South Africa against the Boers. He died in London on 21st January 1914. His peerage passed to his only child, Margaret Charlotte Howard.