Beyond the Mississippi all that was really well known was the territory in the immediate neighbourhood of the little French villages near the mouth of the Missouri. The creole traders of these villages, and an occasional venturous American, had gone up the Mississippi to the country of the Sioux and the Mandans, where they had trapped and hunted and traded for furs with the Indians. At the northern most points that they reached they occasionally encountered traders who had travelled south or southwesterly from the wintry regions where the British fur companies reigned supreme. The headwaters of the Missouri were absolutely unknown; nobody had penetrated the great plains, the vast seas of grass through which the Platte, the Little Missouri, and the Yellowstone ran. What lay beyond them, and between them and the Pacific, was not even guessed at. The Rocky Mountains were not known to exist, so far as the territory newly acquired by the United States was concerned, although under the name of "Stonies" their northern extensions in British America were already down on some maps. The National Government Undertakes the Work. The West had passed beyond its first stage of uncontrolled individualism. Neither exploring nor fighting was thenceforth to be the work only of the individual settlers. The National Government was making its weight felt more and more in the West, because the West was itself becoming more and more an important integral portion of the Union. The work of exploring these new lands fell, not to the wild hunters and trappers, such as those who had first explored Kentucky and Tennessee, but to officers of the United States army, leading parties of United States soldiers, in pursuance of the command of the Government or of its representatives. The earliest and most important expeditions of Americans into the unknown country which the nation had just purchased were led by young officers of the regular army. Jefferson Entitled to the Credit. The first of these expeditions was planned by Jefferson himself and authorised by Congress. Nominally its purpose was in part to find out the most advantageous places for the establishment of trading stations with the Indian tribes over which our government had acquired the titular suzerainty; but in reality it was purely a voyage of exploration, planned with intent to ascend the Missouri to its head, and thence to cross the continent to the Pacific. The explorers were carefully instructed to report upon the geography, physical characteristics, and zoology of the region traversed, as well as upon its wild human denizens. Jefferson was fond of science, and in appreciation of the desirability of non-remunerative scientific observation and investigation he stood honorably distinguished among the public men of the day. To him justly belongs the credit of originating this first exploring expedition ever undertaken by the United States Government. Lewis and Clark Chosen.