All of these tribes gravitated toward the great watercourses, as man, in every stage of his history has done. It was not in this case the use of the stream as a transportation route that made it attractive. The Missouri Valley tribes, unlike those of the Great Lakes, or the Coast, or the northern rivers, were not good navigators. The stream was a treacherous one, and its shores did not yield a timber suitable to the crude workmanship of the Indian. Skin boats were used to a limited extent, but as a rule the horse and not the boat was the means of travel and transportation. The great importance of the river arose from other considerations. In a region where streams are scarce and where most of them dry up in the summer, this river furnished a never-failing supply of as healthy a drinking water as flows on the surface of the globe. Then its valley was the only timbered region of consequence for hundreds of miles on either side. Groves of cottonwood, walnut, cedar, and willow lined its banks, and the Indian here found all the wood that his simple order of life required. The abundant groves along the bottoms gave splendid shelter from the heat of summer and the cold of winter. [Sidenote: STRANGE VISITORS.] The entire watershed of the river was thus originally occupied by Indians. Considering its extensive area, their numbers were very few--scarcely one to ten square miles. But as they mostly dwelt near the rivers, the country seemed to the early navigators more densely populated than it really was. Into this primeval domain there came, more than two centuries ago, strange visitors who never went away. They were welcomed at first; but every foot of ground they gained was held, farther and farther up the river to its source among the mountains, thence to the River of the West, and down its rugged valleys to the western sea. It was a sad day to the tribes of the Missouri Valley, as to every other, when the white man came, but a far sadder day when the emigrant and settler came. Between these two epochs there was a long interval in which the paleface and his red brother lived in comparative harmony together. It was the era of the trader. Under the fur-trade régime the Indian might have continued his native mode of life indefinitely. The trader never sought to change it. He introduced but few innovations; had no desire to introduce any; and looked with as jealous an eye as the Indian himself upon the approach of civilization. This relation of the two races was ideal, and during its continuance the Indian is seen at his best. [Sidenote: THE COMING OF THE EMIGRANT.]