The Louisiana Purchase: Indian and American Sovereignty in the Missouri Watershed

Abstract

Like a historical mantra repeated time and again, it is asserted that the Louisiana Purchase doubled the size of the United States. As this assertion takes for granted that the Purchase included the entire Missouri watershed, it rests on the assumption that France had a valid title thereto because, as a matter of common sense and international law, France could only convey title to territory that it actually owned. But what basis is there for the assumption that France had sovereign title to the vast territory drained by the Missouri River that stretches from the Mississippi River to the Rocky Mountains? In actual fact, at the time of the Purchase in 1803 most of that territory had not even been explored, let alone possessed, by the French – it was occupied and controlled by many Indian nations, over whom France exercised no authority. As France clearly did not exercise de facto sovereignty over the Missouri watershed, any claim it had to the vast territory would have had to be a claim to de jure sovereignty based on law that did not depend on actual occupation and control. If so, what system of law could have given France legal title to this immense territory, most of which no Frenchman had ever laid eyes on?