He was the youngest son of Major Peter MacDougall (1774-1861), of the 25th Regiment of Foot, by his second wife, Elizabeth Stancomb.
In the 1850s, his family moved to Outremont, Canada East, joining Campbell's elder half brother, (Dugald) Lorn MacDougall who lived in Montreal.
Through the influence of his elder brother, Lorn, Campbell MacDougall started his career with the Bank of Montreal.
Campbell and St. Clair MacDougall's firm gained an extensive clientele and turned over a large amount of business.
Campbell died aged forty nine, but in his comparatively short life he had achieved distinction in the financial world, serving as Chairman of the Montreal Stock Exchange.