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Place Name
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Missouri
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Place Status (Type)
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river
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Location
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Mississippi, United States, North America
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Latitude
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unknown
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Longitude
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unknown
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Missouri
, river, c.2,565 mi/4,130 km
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 mi/6,020 km, 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 mi/1,502,200 sq km,
including
2,550 sq mi/6,600 sq km
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-mi/16-km 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 (KS), and Iowa before crossing Mo. and entering
the Mississippi R. 17 mi/27 km 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 mi/160 km downstream.
The Yellowstone, Platte, Kansas (KS), and Osage rivers are the Missouri's
chief tributaries. Above Sioux City, Iowa (IA), the Missouri's fluctuating
flow is regulated by 7 major dams (Gavins Point, Fort Randall,
Big Bend, Oahe, Garrison, Fort Peck, and Canyon Ferry) 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/2.7-m channel maintained over the 760-mi/
1,223-km 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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