blackfoot-valley

No area called Montana yet existed, officially or otherwise when Lewis and Clark explored the region. The whole expanse acquired by the United States west of the Mississippi was officially part of the unorganized and most- ly unexplored Territory of Louisiana. Then between 1821 and 1858, the part of it bordering the Mississippi was carved up into the tier of five states from Louisiana to Minnesota, leaving more or less organized territories stretching from today’s Oklahoma to Montana whose boundaries were changed several times by officials drawing and re-drawing lines on the maps in efforts to re- flect changing demographic and political realities. The larger part of Mon- tana, east of the Divide, went through a succession of political changes: from the beginning part of the Louisiana Territory until 1812, then the Missouri Territory until 1821, “Indian Country” which included much of the Great Plains until 1854, the immense Nebraska Territory until 1861, the Dakota Territory until 1862, and the Idaho Territory until 1864, when the land east of the Di- vide finally became the larger part of the newly created Montana Territory. The smaller part of Montana west of the Divide, the part we are most concerned with, did not even become part of the United States until 1846, when half of the Oregon Country south of the 49th parallel was ceded to the U.S. in the treaty with Great Britain. This area became the Oregon Territory POLITICAL CHANGES ON THE LAND 72