From decade to decade distinct advances of the frontier occurred. By the census of 1820[6:2] the settled area included Ohio, southern Indiana and Illinois, southeastern Missouri, and about one-half of Louisiana. This settled area had surrounded Indian areas, and the management of these tribes became an object of political concern. The frontier region of the time lay along the Great Lakes, where Astor's American Fur Company operated in the Indian trade,[6:3] and beyond the Mississippi, where Indian traders extended their activity even to the Rocky Mountains; Florida also furnished frontier conditions. The Mississippi River region was the scene of typical frontier settlements.[7:1] The rising steam navigation[7:2] on western waters, the opening of the Erie Canal, and the westward extension of cotton[7:3] culture added five frontier states to the Union in this period. Grund, writing in 1836, declares: "It appears then that the universal disposition of Americans to emigrate to the western wilderness, in order to enlarge their dominion over inanimate nature, is the actual result of an expansive power which is inherent in them, and which by continually agitating all classes of society is constantly throwing a large portion of the whole population on the extreme confines of the State, in order to gain space for its development. Hardly is a new State or Territory formed before the same principle manifests itself again and gives rise to a further emigration; and so is it destined to go on until a physical barrier must finally obstruct its progress."[7:4] In the middle of this century the line indicated by the present eastern boundary of Indian Territory, Nebraska, and Kansas marked the frontier of the Indian country.[8:1] Minnesota and Wisconsin still exhibited frontier conditions,[8:2] but the distinctive frontier of the period is found in California, where the gold discoveries had sent a sudden tide of adventurous miners, and in Oregon, and the settlements in Utah.[8:3] As the frontier had leaped over the Alleghanies, so now it skipped the Great Plains and the Rocky Mountains; and in the same way that the advance of the frontiersmen beyond the Alleghanies had caused the rise of important questions of transportation and internal improvement, so now the settlers beyond the Rocky Mountains needed means of communication with the East, and in the furnishing of these arose the settlement of the Great Plains and the development of still another kind of frontier life. Railroads, fostered by land grants, sent an increasing tide of immigrants into the Far West. The United States Army fought a series of Indian wars in Minnesota, Dakota, and the Indian Territory.