After studying at McGill University in Montreal, Morris was called to the bar in 1851. He entered politics 10 years later, when he was elected to the legislature of the united province of Canada as Conservative member for Lanark, a seat he held through Confederation (1867) until 1872. He was an advocate of Confederation and wrote pamphlets supporting it. From 1869 to 1872 he served as the dominion's minister of inland revenue in Sir John A. Macdonald's administration. In 1872 he was appointed chief justice of the Manitoba Court of Queen's Bench. Later that year he was made lieutenant governor of Manitoba and the Northwest Territories, in which post he served for five years before returning to Ontario. From 1878 to 1886 he represented East Toronto in the Ontario legislature.