MISSOURI, a very large river of the United States, which unites with the Mississippi a little beyond the thirtieth degree of north lat. It originates in the Rocky Mountains, and takes the name of Missouri in lat. 45. 10. north, and in long. 110. west, where the three branches, Jefferson, Galatin, and Madison unite. These head branches of the Missouri are navigable to a considerable extent before their junction. Where the river makes its escape from the Rocky Mountains, it presents a spectacle of rare sublimity. For a distance of about six miles the rocks rise 1200 feet perpendicularly from the water's edge. The river is considerably diminished in width where it rushes through these gates of the Rocky Mountains. One hundred and ten miles below this chasm are the stupendous cataracts of the Missouri, one of which has a perpendicular fall of eighty-seven feet, but according to Mr Flint of ninety-eight feet. For about seventeen miles the river may be termed a series of cataracts. Not far below these falls Maria's River from the north joins the Missouri. It is a considerable stream, as are also the Dearborn, Fancy, Manoles, Big Dry, and others, which enter still farther down. Below
these the Missouri receives the waters of the Roche Jaune or Yellow Stone, probably its largest tributary. It rises in the same ranges of mountains as the main river, and in many respects resembles it. It is a broad, deep, and sweeping stream, and at its junction appears to be the larger of the two, entering from the south by a mouth of 850 yards wide. Its course is commonly calculated at 1600 miles, and its entrance is said to be 1880 miles above the mouth of the Missouri. It was selected by the government as an eligible situation for a military post and an extensive settlement. At the junction of the Yellow Stone, the Missouri has wide and fine bottoms, but unfortunately its banks are almost destitute of timber, which will retard its settlement for a long time. A great many rivers join the Missouri below this. The following are the most considerable: Knife River; Cannon-Ball River, which is 140 yards wide; Chienne, which is boatable 800 miles; Poncas, Qui-Courre, White Stone, Big Sioux, Floyd's, and many other streams, all enter on the south side. La Platte, which has a longer course than any tributary of the Missouri, comes in from the south side. It rises in the same ranges of mountains which give birth to the parent stream, and, measured by its meanders, is supposed to have a course of 2000 miles before it joins the principal stream. It is nearly a mile in width at its entrance; but, as its name imports, is shallow, and not boatable except at its highest flood. Kansas, a large tributary from the south, has a course of 1200 miles, and is boatable nearly the whole of its course. From the north side, the following, amongst other streams, flow into the Missouri: the Grand River, which is large, long, deep, and boatable for a great distance; the Nowada, Little Platte, Charatous, Bonne Femme, and Manitou.
The whole length of the Missouri, above its junction with the Mississippi, has been estimated at above 3100 miles. Add to this the distance from the mouth of the Missouri to the Gulf of Mexico, and the total will be nearly 4400 miles. The Missouri is much longer than the Mississippi before their junction, and has a much greater volume of water. It is about half a mile in breadth at its mouth, but is wider in a great part of its course. (R. N. R.)