Discovery of the sources of the Mississippi River : Summary Narrative of an Exploratory Expedition to the Sources of the Mississippi River in 1820. Discovery of the sources of the Mississippi River : Summary Narrative of an Exploratory Expedition to the Sources of the Mississippi River in 1820. Resumed and Completed, by the Discovery of its Origin in Itasca Lake, in 1832 The following pages embrace the substance of the narratives of two distinct expeditions for the discovery of the sources of the Mississippi River, under the authority of the United States. By connecting the incidents of discovery, and of the facts brought to light during a period of twelve years, unity is preserved in the prosecution of an object of considerable importance in the progress of our geography and natural history, at least, from the new impulse which they received after the treaty of Ghent. Geographers deem that branch of a river as its true source which originates at the remotest distance from its mouth, and, agreeably to this definition, the combined narratives, to which attention is now called, show this celebrated stream to arise in Itasca Lake, the source of the Itasca River. Owing to the time which has intervened since these expeditions were undertaken, a mere revision of the prior narrations, in the journal form, was deemed inexpedient. A concise summary has, therefore, been made, preserving whatever information it was thought important to be known or remembered, and omitting all matters not partaking of permanent interest.