A few years after the English war the United States had erected a fort at the junction of the St. Peter's and the Mississippi, near the present city of St. Paul. In 1805, Zebulon Montgomery Pike had treated with the Sioux tribes at this point, and by 1824 the new post had received the name Fort Snelling, which it was to retain until after the admission of Minnesota as a state. Pike and his followers had worked their way up the Mississippi from St. Louis or Prairie du Chien in skiffs or keelboats, and had found little of consequence in the way of white occupation save a few fur-trading posts and the lead mines of Du Buque. Until after the English war, indeed, and the admission of Illinois, there had been little interest in the country up the river; but during the early twenties the lead deposits around Du Buque's old claim became the centre of a business that soon made new treaty negotiations with the northern Indians necessary.

On both sides of the Mississippi, between the mouths of the Wisconsin and the Rock, lie the extensive lead fields which attracted Du Buque in the days of the Spanish rule, and which now in the twenties induced an American immigration. The ease with which these diggings could be worked and the demand of a growing frontier population for lead, brought miners into the borderland of Illinois, Wisconsin, and Iowa long before either of the last states had acquired name or boundary or the Indian possessors of the soil had been satisfied and removed. The nations of Winnebago, Sauk and Foxes, and Potawatomi were most interested in this new white invasion, while all were reluctant to yield the lands to the incoming pioneers. The Sauk and Foxes had given up their claim to nearly all the lead country in 1804; the Potawatomi ceded portions of it in 1829; and the Winnebago in the same year made agreements covering the mines within the present state of Wisconsin.

Gradually in the later twenties the pioneer miners came in, one by one. From St. Louis they came up the great river, or from Lake Michigan they crossed the old portage of the Fox and Wisconsin. The southern reënforcements looked much to Fort Armstrong on Rock Island for protection. The northern, after they had left Fort Howard at Green Bay, were out of touch until they arrived near the old trading post at Prairie du Chien. War with the Winnebago in 1827 was followed in 1828 by the erection of another United States fort,—at the portage, and known as Fort Winnebago. Thus the United States built forts to defend a colonization which it prohibited by law and treaty.

The individual pioneers differed much in their morals and their cultural antecedents, but were uniform in their determination to enjoy the profits for which they had risked the dangers of the wilderness. Notable among them, and typical of their highest virtues, was Henry Dodge, later governor of Wisconsin, and representative and senator for his state in Congress, but now merely one of the first in the frontier movement. It is related of him that in 1806 he had been interested in the filibustering expedition of Aaron Burr, and had gone as far as New Madrid, to join the party, before he learned that it was called treason. He turned back in disgust. "On reaching St. Genevieve," his chronicler continues, "they found themselves indicted for treason by the grand jury then in session. Dodge surrendered himself, and gave bail for his appearance; but feeling outraged by the action of the grand jury he pulled off his coat, rolled up his sleeves, and whipt nine of the jurors; and would have whipt the rest, if they had not run away." With such men to deal with, it was always difficult to enforce unpopular laws upon the frontier. Dodge had no hesitation in settling upon his lead diggings in the mineral country and in defying the Indian agents, who did their best to persuade him to leave the forbidden country. On the west bank of the Mississippi federal authority was successful in holding off the miners, but the east bank was settled between Galena and Mineral Point before either the Indian title had been fully quieted, or the lands had been surveyed and opened to purchase by the United States.

The Indian war of 1827, the erection of Fort Winnebago in 1828, the cession of their mineral lands by the Winnebago Indians in 1829, are the events most important in the development of the first settlements in the new Northwest. In 1829 and 1830 pioneers came up the Mississippi to the diggings in increasing numbers, while farmers began to cast covetous eyes upon the prairies lying between Lake Michigan and the Mississippi. These were the lands which the Sauk and Fox tribes had surrendered in 1804, but over which they still retained rights of occupation and the chase until Congress should sell them. The entry of every American farmer was a violation of good faith and law, and so the Indians regarded it. Their largest city and the graves of their ancestors were in the peninsula between the Rock and the Mississippi, and as the invaders seized the lands, their resentment passed beyond control. The Black Hawk War was the forlorn attempt to save the lands. When it ended in crushing defeat, the United States exercised its rights of conquest to compel a revision of the treaty limits.

The great treaties of 1832 and 1833 not only removed all Indian obstruction from Illinois, but prepared the way for further settlement in both Wisconsin and Iowa. The Winnebago agreed to migrate to the Neutral Strip in Iowa, the Potawatomi accepted a reserve near the Missouri River, while the Black Hawk purchase from the offending Sauk and Foxes opened a strip some forty miles wide along the west bank of the Mississippi. These Indian movements were a part of the general concentrating policy made in the belief that a permanent Indian frontier could be established. After the Black Hawk War came the creation of the Indian Bureau, the ordering of the great western road, and the erection of a frontier police. Henry Dodge was one of the few individuals to emerge from the war with real glory. His reward came when Congress formed a regiment of dragoons for frontier police, and made him its colonel. In his regiment he operated up and down the long frontier for three years, making expeditions beyond the line to hold Pawnee conferences and meetings with the tribes of the great plains, and resigning his command only in time to be the first governor of the new territory of Wisconsin, in 1836. He knew how little dependence could be placed on the permanency of the right wing of the frontier. "Nor let gentlemen forget," he reminded his colleagues in Congress a few years later, "that we are to have continually the same course of settlements going on upon our border. They are perpetually advancing westward. They will reach, they will cross, the Rocky Mountains, and never stop till they have reached the shores of the Pacific. Distance is nothing to our people.... [They will] turn the whole region into the happy dwellings of a free and enlightened people."

The Black Hawk War and its resulting treaties at once quieted the Indian title and gave ample advertisement to the new Northwest. As yet there had been no large migration to the West beyond Lake Michigan. The pioneers who had provoked the war had been few in number and far from their base upon the frontier. Mere access to the country had been difficult until after the opening of the Erie Canal, and even then steamships did not run regularly on Lake Michigan until after 1832. But notoriety now tempted an increasing wave of settlers. Congress woke up to the need of some territorial adjustment for the new country.

Ever since Illinois had been admitted in 1818, Michigan had been the one remaining territory of the old Northwest, including the whole area north of Ohio, Indiana, and Illinois, and extending from Lake Huron to the Mississippi River. Her huge size was admittedly temporary, but as no large centre of population existed outside of Detroit, it was convenient to simplify the federal jurisdiction in this fashion. The lead mines on the Mississippi produced a secondary centre of population in the late twenties and pointed to an early division of Michigan. But before this could be accomplished the Black Hawk purchase had carried the Mississippi centre of population to the right bank of the river. The American possessions on this bank, west of the river, had been cast adrift without political organization on the admission of Missouri in 1821. Now the appearance of a vigorous population in an unorganized region compelled Congress to take some action, and thus, for temporary purposes, Michigan was enlarged in 1834. Her new boundary extended west to the Missouri River, between the state of Missouri and Canada. The new Northwest, which may be held to include Iowa, Wisconsin, and Minnesota, started its political history as a remote settlement in a vast territory of Michigan, with its seat of government at Detroit. Before it was cut off as the territory of Wisconsin in 1836 much had been done in the way of populating it.

The boom of the thirties brought Arkansas and Michigan into the Union as states, and started the growth of the new Northwest. The industrial activity of the period was based on speculation in public lands and routes of transportation. America was transportation mad. New railways were building in the East and being projected West. Canals were turning the western portage paths into water highways. The speculative excitement touched the field of religion as well as economics, producing new sects by the dozen, and bringing schisms into the old. And population moving already in its inherent restlessness was made more active in migration by the hard times of the East in 1833 and 1834.

The immigrants brought to the Black Hawk purchase and its vicinity, in the boom of the thirties, came chiefly by the river route. The lake route was just beginning to be used; not until the Civil War did the traffic of the upper Mississippi naturally and generally seek its outlet by Lake Michigan. The Mississippi now carried more than its share of the home seekers.