The building was completed in 1931 after three stages of construction. It was built exclusively for the Sun Life Assurance Company of Canada. Although the then-new head office of the Royal Bank of Canada at 360 Saint Jacques Street in Montreal was taller by several floors, the Sun Life Building was at the time the largest building in square footage anywhere in the British Empire. The Sun Life Building went through three different stages of construction, the first one starting as early as 1913, but it was not until 1931 that its main 24-storey tower was erected, thus completing the project.