 In the earlier part of the 19th century the area which is today Minnesota was not recognized as a single entity . The Mississippi River had divided the eastern British / French lands of North America from the western Spanish lands and even after the Louisiana Purchase this was for a time seen as a separation between territories . The division between the U.S. territories in the region and the British territories remained ambiguous until the Anglo @-@ American Convention of 1818 , which set the border with British North America at the 49th parallel west of the Lake of the Woods ( except for a small <unk> of land now dubbed the Northwest Angle ) . Border disputes east of the Lake of the Woods continued until the Webster @-@ <unk> Treaty of 1842 . 
