On reviewing the records of explorers and pioneers and the few traditions which have been preserved, the course of Siouan migration and development becomes clear. In general the movements were westward and northwestward. The Dakota tribes have not been traced far, though several of them, like the Yanktonnai, migrated hundreds of miles from the period of first observation to the end of the eighteenth century; then came the Mandan, according to their tradition, and as they ascended the Missouri left traces of their occupancy scattered over 1,000 miles of migration; next the ȼegiha descended the Ohio and passed from the cis-Mississippi forests over the trans-Mississippi plains-the stronger branch following the Mandan, while the lesser at first descended the great river and then worked up the Arkansas into the buffalo country until checked and diverted by antagonistic tribes. So also the Ɉɔiwe’re, first recorded near the Mississippi, pushed 300 miles westward; while the Winnebago gradually emigrated from the region of the Great Lakes into the trans-Mississippi country even before their movements were affected by contact with white men. In like manner the Hidatsa are known to have flowed northwestward many scores of miles; and the Asiniboin swept more rapidly across the plains from the place of their rebellion against the Yanktonnai, on the Mississippi, before they found final resting place on the Saskatchewan plains 500 or 800 miles away. All of the movements were consistent and, despite intertribal friction and strife, measurably harmonious. The lines of movement, so far as they can be restored, are in full accord with the lines of linguistic evolution traced by Hale and Dorsey and Gatschet, and indicate that some five hundred or possibly one thousand years ago the tribesmen pushed over the Appalachians to the Ohio and followed that stream and its tributaries to the Mississippi (though there are faint indications that some of the early emigrants ascended the northern tributaries to the region of the Great Lakes); and that the human flood gained volume as it advanced and expanded to cover the entire region of the plains. The records concerning the movement of this great human stream find support in the manifest reason for the movement; the reason was the food quest by which all primitive men are led, and its end was the abundant fauna of the prairieland, with the buffalo at its head.
While the early population of the Siouan stock, when first the huntsmen crossed the Appalachians, may not be known, the lines of migration indicate that the people increased and multiplied amain during their long journey, and that their numbers culminated, despite external conflict and internal strife, about the beginning of written history, when the Siouan population may have been 100,000 or more. Then came war against the whites and the still more deadly smallpox, whereby the vigorous stock was checked and crippled and the population gradually reduced; but since the first shock, which occurred at different dates in different parts of the great region, the Siouan people have fairly held their own, and some branches are perhaps gaining in strength.