Mackenzie, Sir William, 1849–1923, Canadian railroad builder and financier, b. Ontario. In the early 1870s he became a railroad contractor. He constructed portions of the Canadian National and the Canadian Pacific railroads. Entering (c.1888) into partnership with Sir Donald Mann, another Canadian Pacific contractor, he began the organization and construction of the far-flung network later known as the Canadian Northern Railway, of which Mackenzie became president. Taken over by the Canadian government in 1918, the railroad is now a part of the Canadian National Railway system. Mackenzie was knighted in 1911.