Which parallel separates western Canada from the USA?

The 49th parallel north is a border between the Canadian provinces of British Columbia, Alberta, Saskatchewan and Manitoba (to the north), and the U.S. states of Washington, Idaho, Montana, North Dakota and Minnesota (to the south).

Roughly 3,500 kilometres (2,175 mi) of the Canada–United States border was designated to follow the 49th parallel from British Columbia to Manitoba on the Canada side, and from Washington to Minnesota on the U.S. side, more specifically from the Strait of Georgia to the Lake of the Woods. This international border was specified in the Anglo-American Convention of 1818 and the Oregon Treaty of 1846. However the border as indicated by survey markers placed in the 19th century deviates from the 49th parallel by tens of meters.