The autumn of 1825 witnessed at Prairie du Chien the first step towards peace and condensation along the northern frontier. The Erie Canal, not yet opened, had not begun to drain the population of the East into the Northwest, and Indians were in peaceful possession of the lake shores nearly to Fort Wayne. West of Lake Michigan were constant tribal wars. The Potawatomi, Menominee, and Chippewa, first, then Winnebago, and Sauk and Foxes, and finally the various bands of Sioux around the Mississippi and upper Missouri, enjoyed still their traditional hostility and the chase. Governor Clark again, and Lewis Cass, met the tribes at the old trading post on the Mississippi to persuade them to bury the tomahawk among themselves. The treaty, signed August 19, 1825, defined the boundaries of the different nations by lines of which the most important was between the Sioux and Sauk and Foxes, which was later to be known as the Neutral Line, across northern Iowa. The basis of this treaty of Prairie du Chien was temporary at best. Before it was much more than ratified the white influx began, Fort Dearborn at the head of Lake Michigan blossomed out into Chicago, and squatters penetrating to Rock Island in the Mississippi had provoked the war of 1832, in which Black Hawk made the last stand of the Indians in the old Northwest. In the thirties the policy of removal completed the opening of Illinois and Wisconsin to the whites. [Illustration: INDIAN COUNTRY AND AGRICULTURAL FRONTIER, 1840-1841 Showing the solid line of reservation lands extending from the Red River to Green Bay, and the agricultural frontier of more than six inhabitants per square mile.] The policy of removal and colonization urged by Monroe and Calhoun was supported by Congress and succeeding Presidents, and carried out during the next fifteen years. It required two transactions, the acquisition by the United States of western titles, and the persuasion of eastern tribes to accept the new lands thus available. It was based upon an assumption that the frontier had reached its final resting place. Beyond Missouri, which had been admitted in 1821, lay a narrow strip of good lands, merging soon into the American desert. Few sane Americans thought of converting this land into states as had been the process farther east. At the bend of the Missouri the frontier had arrived; there it was to stay, and along the lines of its receding flanks the Indians could be settled with pledges of permanent security and growth. Here they could never again impede the western movement in its creation of new communities and states. Here it would be possible, in the words of Lewis Cass, to "leave their fate to the common God of the white man and the Indian."