MLW became an exclusive Alco design shop and acquired a substantial portion of the Canadian steam locomotive market. The period of railway expansion between 1900 and 1915 was unprecedented in Canada, with many new orders for locomotives from various domestic manufacturers. Protective customs tariffs also discouraged Canadian railways from purchasing American-built locomotives for use in Canada. Several bankrupt private systems, including the Grand Trunk and Canadian Northern, were nationalized in the years 1918–22. Merged with the federally owned Intercolonial, they formed the federal Crown corporation Canadian National Railways. The federal government mandated that the new, larger public company purchase locomotives from all Canadian manufacturers to discourage domination of the market by any one manufacturer.