Harold Innis wrote his PhD thesis on the history of the Canadian Pacific Railway (CPR). The completion of Canada's first transcontinental railway in 1885 had been a defining moment in Canadian history. Innis's thesis, eventually published as a book in 1923, can be seen as an early attempt to document the railway's significance from an economic historian's point of view. It uses voluminous statistics to underpin its arguments. Innis maintains that the difficult and expensive construction project was sustained by fears of American annexation of the Canadian West. Innis argues that "the history of the Canadian Pacific Railroad is primarily the history of the spread of Western civilization over the northern half of the North American continent". As Robert Babe notes, the railway brought industrialization, transporting coal and building supplies to manufacturing sites. It was also a kind of communications medium that contributed to the spread of European civilization. Babe writes that, for Innis, the CPR's equipment "comprised a massive, energy-consuming, fast-moving, powerful, capital-intensive 'sign' dropped into the very midst of indigenous peoples, whose entire way of life was disrupted, and eventually shattered as a result. Communications scholar Arthur Kroker argues that Innis's study of the Canadian Pacific Railway was only the first in which he attempted to demonstrate that "technology is not something external to Canadian being; but on the contrary, is the necessary condition and lasting consequence of Canadian existence". It also reflected Innis's lifelong interest in the exercise of economic and political power. His CPR history ends, for example, with a recounting of Western grievances against economic policies, such as high freight rates and the steep import tariffs designed to protect fledgling Canadian manufacturers. Westerners complained that this National Policy funnelled money from Prairie farmers into the pockets of the Eastern business establishment. "Western Canada", Innis wrote, "has paid for the development of Canadian nationality, and it would appear that it must continue to pay. The acquisitiveness of Eastern Canada shows little sign of abatement."

Answer this question "What is the CPR?" by extracting the answer from the text above.
Canadian Pacific Railroad