The border between
Lake Superior and the
Lake of the Woods in the
Great Lakes region needed clarification because the faulty
Mitchell Map used in the negotiations for the
Treaty of Paris (1783) was inadequate to define the border according to the terms of that British-American treaty. Ambiguity in the map and treaty resulted in
Minnesota's
Arrowhead region being disputed between the two nations years later, and previous negotiations had not resolved the question. The treaty had the border pass through Long Lake, but did not state that lake's location. However, the map showed the lake flowing into Lake Superior near
Isle Royale, which is consistent with the
Pigeon River route. The British, however, had previously taken the position that the border should leave Lake Superior at
Fond du Lac (the "head of the lake") in modern
Duluth, Minnesota, proceed up the
Saint Louis and
Embarrass rivers, across the
height of land, and down
Pike River and
Lake Vermilion to the
Rainy River. To counter this western route, the U.S. side advocated for an eastern route, used by early French explorer
Jacques de Noyon in 1688, and later a well-used fur traders' route after 1802. This way headed north from the lake at the site of
Fort William up the
Kaministiquia and
Dog Rivers to Cold Water Lake, crossed the divide by Prairie Portage to Height of Land Lake, then went west by way of the Savanne,
Pickerel, and Maligne rivers to Lake La Croix, where it joined the present international border. The Mitchell map had shown both of those routes, and also showed the "Long Lake" route between them. Long Lake was thought to be the Pigeon River (despite the absence of a lake at its mouth). The traditional traders' route left the lake at
Grand Portage and went overland to the Pigeon, up that river and a tributary across the
Height of Land Portage, and thence down tributaries of the Rainy River to Lac La Croix, Rainy Lake and River, and Lake of the Woods. This is finally the route the treaty designated as the border. The treaty clarified the channel that the border would follow between Lake Huron and Lake Superior, awarding
Sugar Island to the U.S. Another clarification made in this treaty resulted in clarifying the anomaly of the
Northwest Angle. Again, due to errors on the Mitchell Map, the Treaty of Paris reads "... through the Lake of the Woods to the most northwesternmost point thereof, and from thence on a due west course to the river Mississippi ..." In fact, a course due west from the Lake of the Woods never intersects the Mississippi. The
Anglo-American Convention of 1818 defined the boundary of Lake of the Woods to the Rocky Mountains. This 1842 treaty reaffirmed the border and further defined it by modifying the border definition to instead read as: The Webster–Ashburton Treaty failed to deal with the
Oregon question, although the issue was discussed in negotiations. ==Other issues==