The Treaty of 1818 saw expansion of both British North America and the US, where the boundary extended westward along the 49th parallel, from the Northwest Angle at Lake of the Woods to the Rocky Mountains. The treaty extinguished British claims to the south of that line up to the Red River Valley, which was part of Rupert's Land. The treaty also extinguished U.S. claims to land north of that line in the watershed of the Missouri River, which was part of the Louisiana Purchase.