The Upper Mississippi River is the portion of the

Mississippi River The Mississippi River is the main stem, primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri River, Missouri. From its traditional source of Lake Ita ...

upstream of

St. Louis St. Louis ( , sometimes referred to as St. Louis City, Saint Louis or STL) is an independent city in the U.S. state of Missouri. It lies near the confluence of the Mississippi and the Missouri rivers. In 2020, the city proper had a populatio ...

Missouri Missouri (''see #Etymology and pronunciation, pronunciation'') is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Ranking List of U.S. states and territories by area, 21st in land area, it border ...

, United States, a city at the confluence of its main tributary, the

Missouri River The Missouri River is a river in the Central United States, Central and Mountain states, Mountain West regions of the United States. The nation's longest, it rises in the eastern Centennial Mountains of the Bitterroot Range of the Rocky Moun ...

. Historically, it may refer to the area above the

Arkansas Post The Arkansas Post (; ), officially the Arkansas Post National Memorial, was the first European colonization of the Americas, European settlement located along the Mississippi River, in the Mississippi Alluvial Plain, and in the present-day U. ...

, above the confluence of

Ohio River The Ohio River () is a river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing in a southwesterly direction from Pittsburgh, Pennsylvania, to its river mouth, mouth on the Mississippi Riv ...

, or above Cape Girardeau.

History

In terms of geologic and hydrographic history, the Upper Mississippi east and south of

Fort Snelling Fort Snelling is a former military fortification and National Historic Landmark in the U.S. state of Minnesota on the bluffs overlooking the confluence of the Minnesota and Mississippi Rivers. The military site was initially named Fort Saint An ...

is a portion of the now-extinct Glacial River Warren which carved the valley of the

Minnesota River The Minnesota River () is a tributary of the Mississippi River, approximately 332 miles (534 km) long, in the U.S. state of Minnesota. It drains a watershed of in Minnesota and about in South Dakota and Iowa. It rises in southwestern ...

, permitting the immense Glacial Lake Agassiz to join the world's oceans at the

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

. The collapse of ice dams holding back Glacial Lake Duluth and Glacial Lake Grantsburg carved out the Dalles of the St. Croix River at

Interstate Park Interstate Park comprises two adjacent state parks on the Minnesota–Wisconsin border, both named Interstate State Park. They straddle ''the Dalles'' of the St. Croix River (Wisconsin-Minnesota), St. Croix River, a deep basalt gorge with gian ...

. The Upper Mississippi River valley likely originated as an ice-marginal stream during the Pre-Illinoian Stage. The

Driftless Area The Driftless Area, also known as Bluff Country and the Paleozoic Plateau, is a topographic and cultural region in the Midwestern United States that comprises southwestern Wisconsin, southeastern Minnesota, northeastern Iowa, and the extreme ...

is a portion of

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

left unglaciated at that ice age's height, hence not smoothed out or covered over by previous geological processes.

Characteristics

The Upper Mississippi from below St. Anthony Falls (

Minneapolis Minneapolis is a city in Hennepin County, Minnesota, United States, and its county seat. With a population of 429,954 as of the 2020 United States census, 2020 census, it is the state's List of cities in Minnesota, most populous city. Locat ...

Minnesota Minnesota ( ) is a U.S. state, state in the Upper Midwestern region of the United States. It is bordered by the Canadian provinces of Manitoba and Ontario to the north and east and by the U.S. states of Wisconsin to the east, Iowa to the so ...

) downstream to St. Paul, Minnesota is a

gorge A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosion, erosive activity of a river over geologic time scales. Rivers have a natural tend ...

with high limestone bluffs carved by the glacial

River Warren Falls The River Warren Falls was a massive waterfall on the glacial River Warren initially located in present-day Saint Paul, Minnesota, United States. The waterfall was across and high. Geologic history The area now occupied by the Twin Cities o ...

. Upstream of St. Anthony Falls, the land slopes gently to river's edge. Downstream of downtown St. Paul, the river enters its wide preglacial valley. The states of

Wisconsin Wisconsin ( ) is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest of the United States. It borders Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michig ...

and

Iowa Iowa ( ) is a U.S. state, state in the upper Midwestern United States, Midwestern region of the United States. It borders the Mississippi River to the east and the Missouri River and Big Sioux River to the west; Wisconsin to the northeast, Ill ...

, along with the federal government, have preserved certain areas of the land along this reach of the river. There are three

National Park Service The National Park Service (NPS) is an List of federal agencies in the United States, agency of the Federal government of the United States, United States federal government, within the US Department of the Interior. The service manages all List ...

sites along the Upper Mississippi River. The

Mississippi National River and Recreation Area The Mississippi National River and Recreation Area is a and protected corridor along the Mississippi River through Minneapolis–Saint Paul in the U.S. state of Minnesota, from the cities of Dayton and Ramsey to just downstream of Hastings. Th ...

is the National Park Service site dedicated to protecting and interpreting the Mississippi River itself. The other two National Park Service sites along the river are:

Effigy Mounds National Monument Effigy Mounds National Monument preserves more than 200 prehistoric mounds built by pre-Columbian Mound Builder cultures, mostly in the first millennium CE, during the later part of the Woodland period of pre-Columbian North America. Numerous ...

and the

Gateway Arch National Park Gateway Arch National Park is a List of national parks of the United States, national park of the United States located in St. Louis, Missouri, near the starting point of the Lewis and Clark Expedition. In its initial form as a List of nationa ...

(home to the

Gateway Arch The Gateway Arch is a monument in St. Louis, Missouri, United States. Clad in stainless steel and built in the form of a weighted catenary Catenary arch, arch, it is the world's tallest arch and List of tallest buildings in Missouri, Missouri's ...

). Unlike the Lower Mississippi, much of the upper river is a series of pools created by a system of 29 locks and

dams A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, ...

. The structures were authorized by

Congress A congress is a formal meeting of the representatives of different countries, constituent states, organizations, trade unions, political parties, or other groups. The term originated in Late Middle English to denote an encounter (meeting of ...

in the 1930s, and most were completed by 1940. A primary reason for damming the river is to facilitate

barge A barge is typically a flat-bottomed boat, flat-bottomed vessel which does not have its own means of mechanical propulsion. Original use was on inland waterways, while modern use is on both inland and ocean, marine water environments. The firs ...

transportation. The dams regulate water levels for the Upper River and play a major part in regulating levels on the Lower Mississippi.

Ecology

On the upper reaches near the Minnesota-

border, the river's

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...

is between 1.5 and 5 kilometers (between 1 and 3 mi) wide. South of

St. Louis, Missouri St. Louis ( , sometimes referred to as St. Louis City, Saint Louis or STL) is an Independent city (United States), independent city in the U.S. state of Missouri. It lies near the confluence of the Mississippi River, Mississippi and the Miss ...

, the alluvial floodplain is approximately 80 kilometers (50 mi) wide. Major

tributaries A tributary, or an ''affluent'', is a stream or river that flows into a larger stream ('' main stem'' or ''"parent"''), river, or a lake. A tributary does not flow directly into a sea or ocean. Tributaries, and the main stem river into which the ...

to the Upper Mississippi River include the

Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. It borders on Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash River, Wabash and Ohio River, Ohio rivers to its ...

, St. Croix, Chippewa,

Black Black is a color that results from the absence or complete absorption of visible light. It is an achromatic color, without chroma, like white and grey. It is often used symbolically or figuratively to represent darkness.Eva Heller, ''P ...

, and

Kaskaskia The Kaskaskia were a historical Indigenous people of the Northeastern Woodlands. They were one of about a dozen cognate tribes that made up the Illiniwek Confederation, also called the Illinois Confederation. Their longstanding homeland was in ...

Rivers. The Upper Mississippi provides habitat for more than 125 fish species and 30 species of freshwater mussels. Three national wildlife refuges along the river cover a total of 465 square kilometers (285,000 ac). The largest of them, the

Upper Mississippi River National Wildlife and Fish Refuge The Upper Mississippi River National Wildlife and Fish Refuge is a , See also * Izaak Walton League * List of National Wildlife Refuges *Trempealeau National Wildlife Refuge Trempealeau National Wildlife Refuge is a National Wildlife Refuge ...

, is over 420 kilometers (260 mi) long, reaching from the

Alma, Wisconsin Alma is a city in and the county seat of Buffalo County, Wisconsin, United States. The population was 716 at the 2020 census. History Alma was named in commemoration of the Battle of Alma, in the Crimean War. Geography Alma is located on ...

area down to

Rock Island, Illinois Rock Island is a city in Rock Island County, Illinois, United States, and its county seat. The population was 37,108 at the 2020 United States census, 2020 census. Located at the confluence of the Rock River (Mississippi River tributary), Rock a ...

. The refuge consists of blufflands, marshes, bottomland forest, islands, channels, backwater lakes and sloughs. It is part of the

Mississippi Flyway The Mississippi Flyway is a bird migration route that generally follows the Mississippi, Missouri, and Lower Ohio Rivers in the United States across the western Great Lakes to the Mackenzie River and Hudson Bay in Canada. The main endpoints of t ...

. Although the river is much cleaner than it was in recent decades, water quality is still a priority concern. Agricultural runoff, including sediment, excessive nutrients, (particularly nitrogen and phosphorus), and chemicals from agricultural and industrial sources continue to threaten Upper Mississippi River aquatic resources. In addition new threats continue to emerge such as personal care items including pharmaceuticals and endocrine-disrupting chemicals. The five states bordering the Upper Mississippi River are working together to address water quality issues. The Minnesota Pollution Control Agency planned to test the entire of the river within the state for the first time in 2024. There is general agreement that nutrients are contributing to the Gulf of Mexico dead zone and to

eutrophication Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of organisms that may deplete the oxygen in the water; ie. the process of too many plants growing on the s ...

problems in

Lake Pepin Lake Pepin ( ) is a naturally occurring lake on the Mississippi River on the border between the U.S. states of Minnesota and Wisconsin. It is located in a valley carved by the outflow of an enormous glacial lake at the end of the last Ice Age. ...

, a large natural riverine lake that is part of Pool 4 of the Upper Mississippi River. National and regional efforts are addressing these problems, but nutrient impairment problems are occurring elsewhere in the Upper Mississippi River as well, particularly in off-channel portions. Excessive nutrients contribute to thick floating mats of filamentous

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

duckweed Lemnoideae is a subfamily of flowering aquatic plants, known as duckweeds, water lentils, or water lenses. They float on or just beneath the surface of still or slow-moving bodies of fresh water and wetlands. Also known as bayroot, they arose fr ...

s that have a pronounced negative impact on light penetration and may threaten the growth and persistence of submerged aquatic vegetation that is important for fish and aquatic life, including waterfowl. Efforts to control nutrients from point and non-point sources in the basin have aimed to provide additional benefits.

Navigation

Navigation locks allow towboats, barges, and other vessels to transit the dams. Approximately 1350 kilometers (850 mi), from the

head of navigation The head of navigation is the farthest point above the mouth of a river that can be navigated by ships. Determining the head of navigation can be subjective on many streams, as the point may vary greatly with the size or the draft of the ship b ...

in Mile 858, Minneapolis, Minnesota down to Cairo, has been made suitable for commercial navigation with a depth of 2.75 meters (9 ft). The

agriculture Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created ...

and barge transportation industries have lobbied in the late 20th and early 21st centuries for a multibillion-dollar project to upgrade the aging lock and dam system. Some environmental groups and advocates of budgetary restraint argue that the project lacks economic justification. Each lock and dam complex creates a pool upstream of it. There are 29 locks on the Upper Mississippi maintained by the

U.S. Army The United States Army (USA) is the primary land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of the United Stat ...

Corps of Engineers—from Upper St. Anthony Falls upstream to Chain of Rocks downstream. The locks provide a collective 123 meters (404 ft) of lift.

Expansion proposals for locks

The Army Corps of Engineers has studied expanding locks 20, 21, 22, 24, and 25 on the Upper Mississippi.

List of pools and locks

References

{{Reflist

External links

Upper Mississippi Valley Digital Image Archive
a collection of images of the Mississippi Valley along the Iowa/Illinois border, from the 1860s through the 1950s. Images are from regional library special collections. *Upper