The Convention respecting fisheries, boundary and the restoration of slaves between the United States of America and the United Kingdom of Great Britain and Ireland, also known as the London Convention, Anglo-American Convention of 1818, Convention of 1818, or simply the Treaty of 1818, was an international treaty signed in 1818 between the above parties. Signed during the presidency of James Monroe, it resolved standing boundary issues between the two nations. The treaty allowed for joint occupation and settlement of the Oregon Country, known to the British and in Canadian history as the Columbia District of the Hudson's Bay Company, and including the northern portion of its sister district New Caledonia.
The two nations agreed to a boundary line involving the 49th parallel north, in part because a straight-line boundary would be easier to survey than the pre-existing boundaries based on watersheds. The treaty marked both the United Kingdom's last permanent major loss of territory in what is now the Continental United States and the United States' only permanent significant cession of North American territory to a foreign power. Britain ceded all of Rupert's Land south of the 49th parallel and east of the Continental Divide, including all of the Red River Colony south of that latitude, while the United States ceded the northernmost edge of the Missouri Territory north of the 49th parallel.
The treaty name is variously cited as
"Convention respecting fisheries, boundary, and the restoration of slaves","Convention of Commerce (Fisheries, Boundary and the Restoration of Slaves)",
and "Convention of Commerce between His Majesty and the United States of America".
This article settled a boundary dispute caused by ignorance of actual geography in the boundary agreed to in the 1783 Treaty of Paris that ended the American Revolutionary War. That earlier treaty had placed the boundary between the United States and British possessions to the north along a line going westward from the Lake of the Woods to the Mississippi River. The parties had failed to realize that the river did not extend that far north, so such a line would never meet the river. In fixing this problem, the 1818 treaty inadvertently created an exclave of the United States, the Northwest Angle, which is the small section of the present state of Minnesota that is the only part of the United States outside Alaska north of the 49th parallel.
Article III provided for joint control of land in the Oregon Country for ten years. Both could claim land and both were guaranteed free navigation throughout.
Article IV confirmed the Anglo-American Convention of 1815, which regulated commerce between the two parties, for an additional ten years.
Article V agreed to refer differences over a U.S. claim arising from the Treaty of Ghent, which ended the War of 1812, to "some Friendly Sovereign or State to be named for that purpose." The U.S. claim was for return of, or compensation for, slaves that were in British territory or on British naval vessels when the treaty was signed. The Treaty of Ghent article in question was about handing over property, and the U.S. claimed that these slaves were the property of U.S. citizens.
Article VI established that ratification would occur within at most six months of signing the treaty.