The Grand Trunk was the last significant railway in Canada to be nationalized by the federal government into the Canadian National Railways (CNR). During the run-up period to 1923, while it was well understood that the federal government would force the amalgamation of a number of money-losing railways, including the Canadian Northern Railway and eventually the Grand Trunk, which would require extensive rationalization of trackage. The GTR was itself involved in pruning unnecessary routes and the former-CAR system was not immune. The GTR found it was particularly expensive to operate on the section over the height of land through Algonquin Park known as the Haliburton Highlands. This hilly area required that heavy or long freight trains had to be either "doubled" (separated and pulled in sections over the high point), or required helper locomotives. The GTR found that heavily loaded eastbound trains from Depot Harbour could be routed south around the Haliburton Highlands to eastern Ontario at less expense.