McKinnon joined the Bank of Commerce in 1925 in Cobalt, Ontario at age 14.

In 1945 he was posted to the bank's head office in Toronto as assistant general manager.

[4] At the end of 1965 he relinquished the title of chief executive officer.

He died on 4 August 1975 of a heart attack while swimming at his cottage on Lake Rosseau.

[6] The funeral was held on 8 August at Grace Church on-the-Hill.