On the 21st of July the voyagers reached the mouth of the great river Platte. Captains Lewis and Clarke ascended it for about a mile, and found the current very rapid; rolling over sands, and divided into several channels, none of which, however, appeared to be more than five or six feet deep.
At this place they encamped for several days, in order to dry their provisions, make some oars, prepare an account and make maps of the country through which they had passed. The game they saw here were chiefly deer, turkeys, and grouse; and they obtained an abundance of ripe grapes. During the nights they were much annoyed by wolves. The country behind their camp was a plain, about five miles in extent, one half covered with wood, and the other dry and elevated.
Not far from this place was a settlement of the Pawnee Indians; a race which had once been extremely numerous, but which now consisted of only four bands, comprising, in the whole, about one thousand four hundred persons.
On the 30th of July, the commanders of the expedition directed an encampment to be formed on the southern bank of the river, for the purpose of their waiting the arrival of the chiefs of the Ottoe Indians, with whom an interview had been appointed to take place. From an elevated station near the camp, they had a beautiful view of the river and of the adjoining country. The hunters abundantly supplied them with deer, turkeys, geese, and beavers; and they were well supplied with fish.
A party of fourteen Ottoe and Missouri Indians, came, at sunset, on the 2d of August, accompanied by a Frenchman who had resided among them and acted as an interpreter. The next morning an awning was formed with the mainsail of the largest vessel; and, under this, Captains Lewis and Clarke received them. A speech was made to these Indians, announcing that the territory which they inhabited had been ceded to the American government, and advising them respecting their future conduct towards the Americans. They promised obedience, requested permission to trade with the Americans, asked for a supply of arms, and solicited the mediation of the voyagers, between them and the Mahars, with whom they were then at war. The chiefs were each presented with a medal, to be worn round his neck, some paint, garters, and cloth ornaments of dress: to these were added a canister of gunpowder, a bottle of whiskey, and a few other articles.
Not long after the ceremonies of the council had concluded, the voyagers again embarked. The hills which now extended along the river, were nearly fifteen miles asunder: those on the north were clad with a considerable quantity of timber; but those on the south had only some scattered trees in the ravines or narrow valleys.
On the 5th of August they passed round a peninsula; and, having encamped on the north side of it, Captain Clarke, in pursuing some game, about three hundred and seventy yards from the camp, found himself at a point of the river which they had already passed, and which, by water, was distant nearly twelve miles. Some miles beyond this, on traversing a part of the country, to reach one of the Indian villages, the vegetation was so luxuriant, that the men, who had been sent to explore it, were forced to break their way through grass, sunflowers, thistles, and other plants, more than ten feet high. This village had once consisted of three hundred huts; but, about four years before the voyagers were here, it had been burnt, in consequence of the small-pox having destroyed four hundred of the men, and a great number of women and children. On a hill behind the village were seen the graves of the nation.
The accounts which the voyagers received of the effects of the small-pox among these Indians, were most distressing. They had been a military and a powerful people; but, when they saw their strength wasting before a malady which they were unable to resist, their phrensy was extreme. They burnt their village; and many of them put to death their wives and children, in order to save them from so cruel an affliction, and that they might all go together to the unknown and better country.
A party of Ottoe and Missouri Indians with whom the voyagers had an interview after this, were almost naked, having no covering, except a cloth round their middle, and a loose blanket or buffalo robe thrown over their shoulders.
In one place Captain Lewis noticed that the hills which extended to the edge of the river on the south side, contained alum, copperas, cobalt, (having the appearance of soft isinglass,) pyrites, and sand-stone: the two first very pure. In another cliff, seven miles distant, he observed an alum rock, of dark brown colour, containing, in its crevices, great quantities of cobalt, cemented shells, and red earth. The appearance of these mineral substances enabled him to account for some disorders of the stomach with which his men had of late been much afflicted. They had been in the habit of dipping up the water of the river inadvertently, and drinking it; and he had now no doubt but the sickness was occasioned by a scum which covered its surface along the southern shore. Always after this the men agitated the water, so as to disperse the scum, before they drank of it, and these disorders ceased.