tributary 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 they ...

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 ...

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its so ...

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 ...

drainage basin A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...

Chicago metropolitan area The Chicago metropolitan area, also referred to as Chicagoland, is the largest metropolitan statistical area in the U.S. state of Illinois, and the Midwest, containing the City of Chicago along with its surrounding suburbs and satellite cities. ...

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 ...

Indiana Indiana ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Michigan to the northwest, Michigan to the north and northeast, Ohio to the east, the Ohio River and Kentucky to the s ...

Michigan Michigan ( ) is a peninsular U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, Upper Midwestern United States. It shares water and land boundaries with Minnesota to the northwest, Wisconsin to the west, ...

Peoria, Illinois Peoria ( ) is a city in Peoria County, Illinois, United States, and its county seat. Located on the Illinois River, the city had a population of 113,150 as of the 2020 United States census, 2020 census, making it the List of municipalities in Ill ...

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, H ...

Illinois Country The Illinois Country ( ; ; ), also referred to as Upper Louisiana ( ; ), was a vast region of New France claimed in the 1600s that later fell under Spanish and British control before becoming what is now part of the Midwestern United States. Whi ...

Illinois and Michigan Canal The Illinois and Michigan Canal connected the Great Lakes to the Mississippi River and the Gulf of Mexico. In Illinois, it ran from the Chicago River in Bridgeport, Chicago to the Illinois River at LaSalle-Peru. The canal crossed the Chicago ...

Lake Michigan Lake Michigan ( ) is one of the five Great Lakes of North America. It is the second-largest of the Great Lakes by volume () and depth () after Lake Superior and the third-largest by surface area (), after Lake Superior and Lake Huron. To the ...

Illinois Waterway The Illinois Waterway system consists of of navigable water from the mouth of the Calumet River at Chicago to the mouth of the Illinois River at Grafton, Illinois. Based primarily on the Illinois River, it is a system of rivers, lakes, and cana ...

Kankakee River The Kankakee River is a tributary of the Illinois River, approximately long, in the Corn Belt, Central Corn Belt Plains of northwestern Indiana and northeastern Illinois in the United States. At one time, the river drained one of the largest we ...

Des Plaines River The Des Plaines River ( ) is a river that flows southward for U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map , accessed May 13, 2011 through southern Wisconsin and northern Illinois''American H ...

Ottawa Ottawa is the capital city of Canada. It is located in the southern Ontario, southern portion of the province of Ontario, at the confluence of the Ottawa River and the Rideau River. Ottawa borders Gatineau, Gatineau, Quebec, and forms the cor ...

Mazon River The Mazon River or Mazon Creek (), is a tributary of the Illinois River in the United States. The confluence is near Morris, Illinois. The Mazon River is associated with the Mazon Creek fossils of the Francis Creek Shale, which are also exposed ...

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

Havana Havana (; ) is the capital and largest city of Cuba. The heart of La Habana Province, Havana is the country's main port and commercial center.Spoon River coming from Fulton County, and across from Browning, it is joined by the

Sangamon River The Sangamon River is a principal tributary of the Illinois River, approximately long,U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed May 13, 2011 in central Illinois in the United Sta ...

, which passes through the state capital,

Springfield, Illinois Springfield is the List of capitals in the United States, capital city of the U.S. state of Illinois. Its population was 114,394 at the 2020 United States census, which makes it the state's List of cities in Illinois, seventh-most populous cit ...

. The La Moine River flows into it approximately southwest of Beardstown, which is south of Peoria and Pekin and northwest of Lincoln and Springfield. Near the confluence of the Illinois with the La Moine River, it turns south, flowing roughly parallel to the Mississippi across western Illinois. Macoupin Creek joins the Illinois on the border between Greene and

Jersey Jersey ( ; ), officially the Bailiwick of Jersey, is an autonomous and self-governing island territory of the British Islands. Although as a British Crown Dependency it is not a sovereign state, it has its own distinguishing civil and gov ...

counties, approximately upstream from the confluence with 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 ...

. For the last of its course, the Illinois is separated from the Mississippi River by only about , by a peninsula of land that makes up Calhoun County. The Illinois joins the Mississippi near Grafton, approximately northwest of downtown St. Louis and about upstream from the confluence of 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 ...

and the Mississippi.

Geology

South of Hennepin, the Illinois River follows the ancient channel of the Mississippi River. The Illinoian Stage, about 300,000 to 132,000 years ago, blocked the Mississippi near Rock Island, diverting it into its present channel. After the glacier melted, the Illinois River flowed into the ancient channel. The Hennepin Canal roughly follows the ancient channel of the Mississippi upstream of Rock Island. The modern channel of the Illinois River was shaped in a matter of days by the Kankakee Torrent. During the melting of the Wisconsin Glacier about 18,500 years ago, a lake formed in present-day Indiana, comparable to one of the modern

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, H ...

. The lake formed behind the terminal moraine of a substage of that glacier. Melting ice to the north eventually raised the level of the lake so that it overflowed the moraine. The dam burst, and the entire volume of the lake was released in a very short time, perhaps a few days. Because of the manner of its formation, the Illinois River runs through a deep canyon with many rock formations. It has an "underutilized channel", one far larger than would be needed to contain any conceivable flow of the modern river.

History

The Illinois River valley has long been an important transportation route for civilizations. The portages between the Des Plaines and

Chicago River The Chicago River is a system of rivers and canals with a combined length of that runs through the city of Chicago, including its center (the Chicago Loop). The river is one of the reasons for Chicago's geographic importance: the related Chic ...

s and the Kankakee and St. Joseph rivers allowed Native Americans, Europeans, and later Americans access between the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, H ...

and the

Mississippi basin The Mississippi River is the 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. From its traditional source of Lake Itasca in northern Minnesota, ...

. The first European presence in the area was the

Jesuit The Society of Jesus (; abbreviation: S.J. or SJ), also known as the Jesuit Order or the Jesuits ( ; ), is a religious order (Catholic), religious order of clerics regular of pontifical right for men in the Catholic Church headquartered in Rom ...

mission founded in 1675 by Father

Jacques Marquette Jacques Marquette, Society of Jesus, S.J. (; June 1, 1637 – May 18, 1675), sometimes known as Père Marquette or James Marquette, was a French Society of Jesus, Jesuit missionary who founded Michigan's first European settlement, Sault Ste. M ...

on the banks of the Illinois across from Starved Rock at the Grand Village of the Illinois, near present-day Utica. The Illinois Confederation were the primary inhabitants of the valley. Marquette wrote of the river, "We have seen nothing like this river that we enter, as regards its fertility of soil, its prairies and woods; its cattle, elk, deer, wildcats, bustards, swans, ducks, parroquets, and even beaver. There are many small lakes and rivers. That on which we sailed is wide, deep, and still, for 65 leagues." In 1680,

René-Robert Cavelier, Sieur de La Salle René-Robert Cavelier, Sieur de La Salle (; November 22, 1643 – March 19, 1687), was a 17th-century French explorer and North American fur trade, fur trader in North America. He explored the Great Lakes region of the United States and Canada ...

built the first fort in Illinois, Ft. St. Louis, at Starved Rock to facilitate the fur trade and defend 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 ...

against the

Iroquois The Iroquois ( ), also known as the Five Nations, and later as the Six Nations from 1722 onwards; alternatively referred to by the Endonym and exonym, endonym Haudenosaunee ( ; ) are an Iroquoian languages, Iroquoian-speaking Confederation#Ind ...

. Later the fort was relocated to the present site of Creve Coeur, near Peoria. The French retained a presence in the area, with small trading posts. Prior to the construction of the Illinois & Michigan Canal, completed in 1845, Peoria was the only large settlement on the River. The river's trade flowed downstream to be dominated by St. Louis. After the I&M Canal was built, a string of cities, such as LaSalle, Peru, and Ottawa grew along the river, extending

Chicago Chicago is the List of municipalities in Illinois, most populous city in the U.S. state of Illinois and in the Midwestern United States. With a population of 2,746,388, as of the 2020 United States census, 2020 census, it is the List of Unite ...

's influence into the Mississippi Valley. During the nineteenth and early twentieth centuries, the residents of the river towns were deeply involved in harvesting the river's fish, waterfowl,

mussels Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, whic ...

, and

ice Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 ° C, 32 ° F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally oc ...

. They were economically and culturally dependent on the river, building up industries such as tourism related to duck hunting and sport fishing, commercial fishing, musseling for the button factories, and ice cutting for early attempts at refrigeration for domestic and commercial use. With the construction of the

Chicago Sanitary and Ship Canal The Chicago Sanitary and Ship Canal, historically known as the Chicago Drainage Canal, is a canal system that connects the Chicago River to the Des Plaines River. It reverses the direction of the Main Stem and the South Branch of the Chicago ...

in the late 19th century, Chicago's sewage was pushed down the river rather than into Lake Michigan. As the canal declined by the early 1900s, it was eventually replaced by the

Illinois Waterway The Illinois Waterway system consists of of navigable water from the mouth of the Calumet River at Chicago to the mouth of the Illinois River at Grafton, Illinois. Based primarily on the Illinois River, it is a system of rivers, lakes, and cana ...

in 1933, which is still in use today.

Interpretation

The Peoria Riverfront Museum contains a gallery, "Illinois River Encounter," that offers an interpretation of the river through an aquarium tank, and displays of the river's geology, ecology, social history, engineering, and commercial use. The Starved Rock Lock and Dam Visitor Center features exhibits on the Illinois River with a viewing area of the working lock in a site frequented by bald eagles.

Modern use

From 1905 to 1915, more freshwater fish were harvested from the Illinois River than from any other river in the United States except for the

Columbia River The Columbia River (Upper Chinook language, Upper Chinook: ' or '; Sahaptin language, Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river headwater ...

. The Illinois River was once a major source of

mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and Freshwater bivalve, freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other ...

s for the shell button industry.

Overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing Fish stocks, fish stock), resu ...

, habitat loss from heavy

siltation Siltation is water pollution caused by particulate terrestrial clastic material, with a particle size dominated by silt or clay. It refers both to the increased concentration of suspended sediments and to the increased accumulation (temporary o ...

, and

water pollution Water pollution (or aquatic pollution) is the contamination of Body of water, water bodies, with a negative impact on their uses. It is usually a result of human activities. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and ...

have eliminated most commercial fishing except for a small mussel harvest to provide shells to seed

pearl A pearl is a hard, glistening object produced within the soft tissue (specifically the mantle (mollusc), mantle) of a living Exoskeleton, shelled mollusk or another animal, such as fossil conulariids. Just like the shell of a mollusk, a pear ...

oysters overseas. It is commercially fished downstream of the Rt. 89 bridge at Spring Valley. However, an infestation of invasive Asian carp has crowded out many game fish in the river. The Illinois River is still an important sports fishing waterway with a good sauger fishery. Illinois River aerial

The Illinois forms part of a modern waterway that connects the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, H ...

at

Chicago Chicago is the List of municipalities in Illinois, most populous city in the U.S. state of Illinois and in the Midwestern United States. With a population of 2,746,388, as of the 2020 United States census, 2020 census, it is the List of Unite ...

to the Mississippi River. The waterway was originally established by the building of the

Illinois and Michigan Canal The Illinois and Michigan Canal connected the Great Lakes to the Mississippi River and the Gulf of Mexico. In Illinois, it ran from the Chicago River in Bridgeport, Chicago to the Illinois River at LaSalle-Peru. The canal crossed the Chicago ...

that connected the Illinois River to the

Chicago River The Chicago River is a system of rivers and canals with a combined length of that runs through the city of Chicago, including its center (the Chicago Loop). The river is one of the reasons for Chicago's geographic importance: the related Chic ...

. When the Sanitary District of Chicago later reversed the flow of the Chicago River, the pollution and

sewage Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewerage, sewer system. Sewage consists of wastewater discharged fro ...

of the city of Chicago flowed down into the Illinois River. The Illinois and Michigan Canal has since been replaced by the

Illinois Waterway The Illinois Waterway system consists of of navigable water from the mouth of the Calumet River at Chicago to the mouth of the Illinois River at Grafton, Illinois. Based primarily on the Illinois River, it is a system of rivers, lakes, and cana ...

, including the

Chicago Sanitary and Ship Canal The Chicago Sanitary and Ship Canal, historically known as the Chicago Drainage Canal, is a canal system that connects the Chicago River to the Des Plaines River. It reverses the direction of the Main Stem and the South Branch of the Chicago ...

. River traffic and flood control is managed by eight locks and dams operated by the U.S. Army Corps of Engineers. As of 2011, all locks and dams on this waterway are closed to visitors for security reasons, except the Starved Rock Visitor Center, which offers an excellent interpretation of the entire system. The waterway is heavily used by barges transporting bulk goods such as grain and oil. It is used in the summer and early fall by tourists in pleasure boats cruising the Great Loop. The Illinois River is an important part of the Great Loop, the circumnavigation of Eastern North America by water. The City of Peoria is developing a long-term plan to reduce combined sewer overflows to the Illinois River, as required by the U.S. Environmental Protection Agency and the Illinois Environmental Protection Agency. During dry weather, sewage flows safely through the city's sewers to the Greater Peoria Sanitation District

wastewater treatment plant Wastewater treatment is a process which removes and eliminates contaminants from wastewater. It thus converts it into an effluent that can be returned to the water cycle. Once back in the water cycle, the effluent creates an acceptable impact on ...

. However, about 28 times a year, melting snow or rainwater can overwhelm the sewers, causing untreated sewage to overflow into the Illinois River. Peoria was required to examine the sewer overflows and prepare a long-term control plan to meet

Clean Water Act The Clean Water Act (CWA) is the primary federal law in the United States governing water pollution. Its objective is to restore and maintain the chemical, physical, and biological integrity of the nation's waters; recognizing the primary respo ...

requirements and protect the Illinois River. The city had to submit its plan by December 2008 to U.S. EPA and Illinois EPA. The issue was still under discussion as recently as 2016. The John Hartford song "Long Hot Summer Day" is written from the perspective of a barge worker on the Illinois River. It references the Illinois towns of Pekin, Beardstown, and Alton.

Cities and towns

*

Bath Bath may refer to: * Bathing, immersion in a fluid ** Bathtub, a large open container for water, in which a person may wash their body ** Public bathing, a public place where people bathe * Thermae, ancient Roman public bathing facilities Plac ...

* Beardstown * Browning * Chillicothe *

Chicago Chicago is the List of municipalities in Illinois, most populous city in the U.S. state of Illinois and in the Midwestern United States. With a population of 2,746,388, as of the 2020 United States census, 2020 census, it is the List of Unite ...

* Channahon * Creve Coeur * East Peoria *

Florence Florence ( ; ) is the capital city of the Italy, Italian region of Tuscany. It is also the most populated city in Tuscany, with 362,353 inhabitants, and 989,460 in Metropolitan City of Florence, its metropolitan province as of 2025. Florence ...

* Grafton * Hardin *

Havana Havana (; ) is the capital and largest city of Cuba. The heart of La Habana Province, Havana is the country's main port and commercial center.Hennepin * Henry * Kampsville * Kingston Mines * LaSalle * Lacon *

Liverpool Liverpool is a port City status in the United Kingdom, city and metropolitan borough in Merseyside, England. It is situated on the eastern side of the River Mersey, Mersey Estuary, near the Irish Sea, north-west of London. With a population ...

*

Marseilles Marseille (; ; see below) is a city in southern France, the prefecture of the department of Bouches-du-Rhône and of the Provence-Alpes-Côte d'Azur region. Situated in the Provence region, it is located on the coast of the Mediterranean S ...

* Meredosia * Morris * Naplate *

Naples Naples ( ; ; ) is the Regions of Italy, regional capital of Campania and the third-largest city of Italy, after Rome and Milan, with a population of 908,082 within the city's administrative limits as of 2025, while its Metropolitan City of N ...

* North Utica * Oglesby *

Ottawa Ottawa is the capital city of Canada. It is located in the southern Ontario, southern portion of the province of Ontario, at the confluence of the Ottawa River and the Rideau River. Ottawa borders Gatineau, Gatineau, Quebec, and forms the cor ...

*

Pearl A pearl is a hard, glistening object produced within the soft tissue (specifically the mantle (mollusc), mantle) of a living Exoskeleton, shelled mollusk or another animal, such as fossil conulariids. Just like the shell of a mollusk, a pear ...

* Pekin * Peoria * Peoria Heights *

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

*

Rome Rome (Italian language, Italian and , ) is the capital city and most populated (municipality) of Italy. It is also the administrative centre of the Lazio Regions of Italy, region and of the Metropolitan City of Rome. A special named with 2, ...

* Seneca * Spring Bay * Spring Valley * Valley City

Notes

References

Illinois Glacial History

External links

Hydrography

Geology

History

Interpretation

Modern use

Cities and towns

See also

Notes

References

External links