MISSOURI RIVER (ante), drains an estimated territory of. 500,000 sq. miles. It joins the Mississippi at lat. 38° 50' 50' n., and long. 90° 13' 45' w. from Greenwich. From the point where the Kansas enters it, its course is nearly e., and within the state of Missouri. Its current, in this part of its course, is about 5 m. an hour. The frequenci of snags makes navigation difficult. The banks are thickly covered with w000. Between fort Leavenworth and its mouth three considerable rivers discharge into it—the Kansas, Grand. and Osage, all of which are navigable for 150 to 200 miles. From the Kansas to 40° 38' n. hat. it is the boundary between Missouri and the Indian territory; and thence to the Big Sioux, between the Indian territory and Iowa. The Platte dis chnrges into the Missouri through three channels, its waters having made a delta at its mouth. Before the Platte, at least five smaller streams--the Big and Little Nemaba, the Noda•ay, the Nishnabotana, and the little Tarkio—empty into the Missouri. The
course of the river, from the mouth of the Platte to the Kansas, and from fort Pierre to the Big Sioux. is s.e. Its general direction for the first 500 m. is n.; then it flows p.n.e. till it joins the White Earth, from whose mouth general course is s.e. At a distance of 2,575 m. from its mouth occur the Great falls, where it descends 357 ft. in 16i miles. The highest of these falls is 87 ft., and between and below them is a series of rapids. At a distance of 1216 in. from its mouth it is joined by the Yellowstone, its largest tributary; at 1310 m from its mouth, by the Cheyenne; at 1130 m. from its mouth, by the White; at 853 m., by the Big Sioux: at 600 m., by the Platte; at 340 nt., by the Kansas; at 240 in., by the Grand; and at 133 m., by the Osage. It is subject to two annual floods, one caused by the melting of the snow on the alluvial prairies, and occurring in May; the other, occurring in June, is caused by the melting of the moun tain snows.