A more aggressive/ stronger US government ensures that the
Oregon boundary dispute is settled more in its favor, and the border between the USA and Britain west of the continental divide is set at 51 degrees north (rather than 49). OTL Vancouver is American.
As a result,
Prince Rupert (OTL population 12,000) and
Bella Coola (OTL population 2,000), as the only Canadian ports on the Pacific, end up growing considerably. Prince Rupert has a railway and road built to it earlier than in OTL, and emerges as Canada's primary west coast port. By the present day, Prince Rupert's metropolitan area has around a million people.