In 1867, four British colonies joined to form the Dominion of Canada:

· Canada East (Quebec)

· Canada West (Ontario)

· New Brunswick

· Nova Scotia

However, lands to the west and northwest of Ontario, called Rupert's Land, which were controlled by the Hudson's Bay Company, were not included in the Dominion of Canada. Canadian Prime Minister John A. MacDonald was determined to extend the ownership, control, and authority of the Dominion of Canada over the western territories. Westward expansion was an early Canadian preoccupation. In 1869 the Hudson’s Bay Company agreed to sell to Canada Rupert’s Land and The North-Western Territory, which together became the Northwest Territories. The traditionally autonomous Metis of Red River resisted annexation. They feared that they would lose their land and be overrun by farmers migrating west from Ontario.

The railroad was critical to the success of this westward expansion. British Columbia agreed to join after Canada committed to building a railroad to the Pacific coast within ten years.