Political map of the Arctic & the Far North 15 June 1846 (Oregon Treaty): Following the 1837 rebellions (Rebellions of 1837), the British merged the two Canadas into a single autonomous province (Province of Canada) and set about resolving their border disputes with the United States. The biggest dispute was over the jointly occupied Columbia District or Oregon Country (Oregon dispute), which had been dominated by the Hudson's Bay Company but was now seeing increasing numbers of American settlers (Oregon Trail). Despite originally supporting demands for full annexation, US President James Polk was preparing for war with Mexico (Mexican-American War) and agreed to split the territory with the British (Oregon Treaty).