Final answer:
The last province to join Canada was Newfoundland on March 31, 1949. It was previously a British colony and its inclusion completed Canada's current geographical framework.
Step-by-step explanation:
The last province to join Canada was Newfoundland. On March 31, 1949, Newfoundland transitioned from a British colony to become a province of Canada. Prior to this, the Dominion of Canada had already stretched from the Atlantic to the Pacific. The inclusion of Newfoundland as a province marked the final step in Canada's journey to its current geographic composition. The other provinces mentioned, such as Alberta, Saskatchewan, and British Columbia, joined Canada much earlier, with British Columbia being the last before Newfoundland in 1871, demanding the construction of a transcontinental railroad as a condition for its entry into Confederation, which was completed in 1885.