To discover the true source of any of the great rivers of the world, that is, that one of all sources which measured along the axis of its channel is farthest from its mouth, has ever been an alluring problem to the exploring geographer. David Thompson, geographer of the Northwest Company, in the course of a journey of exploration lasting a year and extending to the Missouri River, on April 23, 1798, reached Turtle Lake, four miles north of Lake Bemidji, and believed himself the discoverer of the true source of the Mississippi. Lieutenant Pike was confident that when on the 12th day of February, 1806, he reached the upper Red Cedar (Cass) Lake he was at the “upper source of the Mississippi.” These claims were either not known or not trusted, and a series of expeditions to reach the “true source” of the Mississippi was begun, soon after the military occupation in 1819. Lewis Cass, known best in American history by his national employments as senator, cabinet officer, and foreign minister, had cut such a figure as colonel of an Ohio regiment and brigadier-general in the War of 1812 that the President made him governor of the Territory of Michigan; an office which he held for seventeen years. That territory in 1819 was extended to the Mississippi River. Its governor was naturally curious to see something of this immense addition to his jurisdiction and the great river forming its western bound. He sought and obtained leave to conduct an expedition. An engineer officer, Captain Douglass, was ordered to join it, and Governor Cass employed Henry R. Schoolcraft, of whom we are to hear later, as mineralogist at one dollar and a half a day. Leaving Detroit late in May, 1820, with ten Indians and seven soldiers, in three birch-bark canoes, Cass was at the American Fur Company’s post at Fond du Lac (of Superior) on the 6th of July. He ascended the St. Louis River and took the Savanna portage to Sandy Lake. With a reduced party he pushed up stream through Lake Winnebigoshish to that upper Red Cedar Lake which Pike had seen fourteen years before. Assured that this was the true source of the Mississippi, he ended his journey. Mr. Schoolcraft doubted, but he was too polite to differ openly with his chief. Captain Douglass on his map gave the lake the name “Cassina,” which, shorn of two superfluous syllables, has remained in use. Mr. Schoolcraft wrote a narrative of the expedition which is very pleasant reading. The return journey, beginning July 22, was down the Mississippi to Prairie du Chien and thence to Green Bay by the Fox-Wisconsin portage. At Fort Snelling the party were feasted with fresh vegetables from the post garden. At the Sioux agency, then on the Mendota side of the Minnesota, some chiefs of the Sioux and Chippeways were got together in council and a reluctant consent was obtained to cease from troubling one another. The high contracting parties were content to gratify the white man, but they understood the farcical nature of the convention. Governor Cass reported the cost of the expedition at $6156.40-1/4.