The author enjoys weaving real people into her novels. Mackenzie is one of the several self-made millionaires that crop up in the book. He was one of the builders of the transcontinental Canadian Northern Railway (CNoR), and also owned the Toronto Street Railway. But the CNoR went into bankruptcy and was taken over by the government, becoming part of the CNR in 1918. There’s an excellent biography about him by Dr. R.B. Fleming. Find out more at this website.