The Grand Trunk Pacific Railway was a 4800 km system whose main line ran from Winnipeg via Melville and Edmonton to Prince Rupert, British Columbia. Incorporated in 1903, it was built between 1906 and 1914 to provide the Grand Trunk Railway with western connections. It was to have assumed responsibility for the government-built National Transcontinental Railway, but financial difficulties prevented this from happening. The Grand Trunk Pacific faced severe competition from the Canadian Pacific Railway and the Canadian Northern Railway, both of which had excellent branch and feeder lines on the prairies. Construction costs, the exigencies of wartime financing, and the lack of a viable system of branch lines brought the Grand Trunk Pacific into receivership. The Grand Trunk, which had guaranteed Grand Trunk Pacific securities, tried to escape its obligations, but eventually the western road also dragged the Grand Trunk into default and nationalization.

The federal government decided in 1919 to acquire both the Grand Trunk Pacific and the Grand Trunk at a price to be established by arbitration, and in 1923 the operations of the Grand Trunk, the Grand Trunk Pacific and the National Transcontinental merged with those of the recently nationalized Canadian Northern Railway to form the new Canadian national railways system.