text: The first part of the US-Canada border was first defined in 1783 with  the Treaty of Paris, that marked the border between the new United States of America from British colonies in North America. Because the area was not well mapped, there were some disputes, and minor skirmishes, until the Webster–Ashburton Treaty in 1842 which fixed the border between Maine and New Bruinswick. As both the US and British-run Canada were exanding westward in the 1840's, there was another dispute on where the US-Canada border would exist in the western part of the continent. The Americans wanted to claim everything south of the parallel of latitude of 54' degrees 40 minutes. (leading to the phrase 54-40 or fight!). In 1846, the Oregon Territory treaty was passed, setting the US-Canada border as a continuation of the 49th parallel (where it was set along the Minnesota border). In 1903, the boundaries of Alaska were set by a US-British-Canadian commission.\n\nThere are still some areas under dispute between the US and Canada - along the Maine/New Brunswick border, and the Yukon/Alaska border (see second link)