Neptune's Needle

c.2,565 miles long (including its Jefferson-Beaverhead-Red Rock headstream), the longest river of the U.S. and the principal tributary of the Mississippi R. The length of the combined Missouri-Mississippi system from the headwaters of the Missouri to the mouth of the Mississippi is c.3,740 miles, making it the world's 3d-longest river after the Nile and the Amazon. The Missouri R. drains an area of c.580,000 sq miles, including 2,550 sq miles in Canada. The principal headwaters of the Missouri are the Jefferson, Madison, and Gallatin rivers, which rise high in the Rocky Mts., SW Mont., and join to form the Missouri near Three Forks, Mont. The Missouri's upper course flows N through scenic mt. terrain including Gate of the Mts., a deep gorge. At Great Falls, Mont., the river enters a 10-mile stretch of cataracts that prevented navigation to the upper river and effectively established Fort Benton, Mont., as the head of navigation for 19th-cent. riverboats. Below Fort Benton, the Missouri follows a meandering course E and then SE across the Great Plains of W-central U.S., crossing Mont., N.Dak., and S.Dak. and forming part of the boundaries of Nebr., Kansas, and Iowa before crossing Mo. and entering the Mississippi R. 17 miles N of St. Louis. Nicknamed "Big Muddy" for its heavy load of silt, the brown waters of the Missouri do not readily mix with the gray waters of the Mississippi until c.100 miles downstream. The Yellowstone, Platte, Kansas, and Osage rivers are the Missouri's chief tributaries. Above Sioux City, Iowa, the Missouri's fluctuating flow is regulated by 7 major dams and more than 80 other dams on tributary streams. These dams, with their reservoirs, are part of the coordinated, basinwide Missouri River basin project (authorized by the U.S. Congress in 1944), which provides for flood control, navigation, hydroelectric power, irrigation water, and recreational facilities. The dams serve to impound for later use the spring rains and snow melt that swell the volume of the river in March and April and also the 2d flood stage that frequently occurs in June as the snow melts in the more remote mt. regions. Because the dams have no locks, Sioux City is the head of navigation for the 9-ft channel maintained over the 760-miles stretch downstream to the Mississippi. Tugboats pushing strings of barges move freight along this route. From Dec. to March, navigation is interrupted by ice and low water levels (resulting from upstream freezing); summer water levels, which frequently fall so low as to cause riverboats to go aground, are now maintained at safe levels by the release of water from Gavins Point Dam. Silt, fertilizers, and pesticides, which are contained in the runoff from agr. lands, and urban areas pollute the river at selected times of the year. The Missouri R. was an important artery of commerce for Native Amer. villages of the Plains culture long before the Fr. explorers Jacques Marquette and Louis Joliet passed the mouth of the river in 1683 and the Canadian explorer Verendrye visited the upper reaches of the river in 1738. David Thompson, a Can. fur trader, explored part of the river in 1797. Meriwether Lewis and William Clark followed the Missouri on their journey (1803-1806) to the Pacific Ocean and described it at length. The 1st steamboat ascended the river in 1819 and hundreds more later navigated the uncertain waters to Fort Benton. Mormons bound for Utah and pioneers bound for Oregon and Calif. followed the Missouri valley and that of the Platte overland to the West. R. traffic declined with the loss of freight to the RR after the Civil War, but it has been revitalized in the 20th cent., in the sect. below Sioux City, through the navigational improvements and flood control efforts of the Missouri R. basin project. The Missouri R. is the water supply for several million persons. Occasional high floods cause considerable damage. The Great Flood of 1993 on the river below Omaha, which set record crests and record discharges, and another flood in 1995, have prompted reevaluation of river management, goals, and strategies.

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Compiler

Peter Richards