 All of the land east of the Mississippi River was granted to the United States by the Second Treaty of Paris at the end of the American Revolution in 1783 . This included what would become modern day Saint Paul but only part of Minneapolis , including the northeast , north @-@ central and east @-@ central portions of the state . The wording of the treaty in the Minnesota area depended on landmarks reported by fur traders , who erroneously reported an " Isle Phelipeaux " in Lake Superior , a " Long Lake " west of the island , and the belief that the Mississippi River ran well into modern Canada . Most of the state was purchased in 1803 from France as part of the Louisiana Purchase . Parts of northern Minnesota were considered to be in Rupert 's Land . The exact definition of the boundary between Minnesota and British North America was not addressed until the Anglo @-@ American Convention of 1818 , which set the U.S. – Canada border at the 49th parallel west of the Lake of the Woods ( except for a small chunk of land now dubbed the Northwest Angle ) . Border disputes east of the Lake of the Woods continued until the Webster @-@ Ashburton Treaty of 1842 . 
