The Iowa River is a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of the Mississippi River

Mississippi River

The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...

 in the state of Iowa

Iowa

Iowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. It is about 323 miles (519.8 km) long and is open to small river craft to Iowa City

Iowa City, Iowa

Iowa City is a city in Johnson County, State of Iowa. As of the 2010 Census, the city had a total population of about 67,862, making it the sixth-largest city in the state. Iowa City is the county seat of Johnson County and home to the University of Iowa...

, about 65 miles (104.6 km) from its mouth. Its major tributary is the Cedar River.

It rises in two branches, the West Branch and East Branch, both of which have their headwaters in Hancock County

Hancock County, Iowa

-2010 census:The 2010 census recorded a population of 11,341 in the county, with a population density of . There were 5,330 housing units, of which 4,741 were occupied.-2000 census:...

, each about 38 miles (61.2 km) long and which join in Belmond

Belmond, Iowa

-2010 census:The 2010 census recorded a population of 2,376 in the county, with a population density of . There were 1,197 housing units, of which 1047 were occupied.-2000 census:...

.

The Iowa then proceeds roughly in a southeast direction, passing through the city of Iowa Falls

Iowa Falls, Iowa

Iowa Falls is a city in Hardin County, Iowa, United States. Iowa Falls is the home of Ellsworth Community College. It is also a regional transportation center, located along U.S. Routes 20 and 65 and the Canadian National and Union Pacific Railroads. The population was 5,193 at the 2000 census. A...

, through a scenic valley to Steamboat Rock

Steamboat Rock, Iowa

Steamboat Rock is a city in Hardin County, Iowa, United States. The population was 336 at the 2000 census.-Geography:Steamboat Rock is located at ....

, then through the cities of Eldora

Eldora, Iowa

Eldora is a city in Hardin County, Iowa, United States. The population was 3,035 at the 2000 census. It is the county seat of Hardin County. Eldora is located adjacent to the Iowa River and Pine Lake State Park. The city is most famous for the filming of the 1996 movie Twister on location. The...

, Marshalltown

Marshalltown, Iowa

Marshalltown is a city in and the county seat of Marshall County, Iowa, United States. The population was 27,552 in the 2010 census, an increase from the 26,009 population in the 2000 census. -History:...

, Tama

Tama, Iowa

Tama is a city in Tama County, Iowa, United States. The population was 2,731 at the 2000 census. Tama is located a few miles from the Meskwaki Settlement, Iowa's only significant Native American community. Tama was located on the historic Lincoln Highway and is home to an original Lincoln Highway...

, and Marengo

Marengo, Iowa

Marengo is a city in and the county seat of Iowa County, Iowa, United States. It has served as the county seat since August 1845, even though it was not incorporated until July 1859. The population was 2,528 in the 2010 census, a decline from 2,535 in the 2000 census. -Geography:Marengo's longitude...

, and through the Amana Colonies

Amana Colonies

The Amana Colonies are a group of settlements of radical German Pietists in Iowa, USA, comprising seven villages. Calling themselves the Ebenezer Society or the Community of True Inspiration , they first settled in New York state near Buffalo in what is now the Town of West Seneca...

 in Iowa County

Iowa County, Iowa

-2010 census:The 2010 census recorded a population of 16,355 in the county, with a population density of . There were 7,258 housing units, of which 6,677 were occupied.-2000 census:...

. In Johnson County

Johnson County, Iowa

-2010 census:The 2010 census recorded a population of 130,882 in the county, with a population density of . There were 55,967 housing units, of which 52,715 were occupied.-2000 census:...

, it becomes impounded by the Coralville Dam in the Coralville Reservoir

Coralville Lake

Coralville Lake is a reservoir formed by Coralville Dam, a dam on the Iowa River just upstream from the city of Coralville, Iowa. Construction started in 1949, was delayed by the Korean War, and finally finished in 1958...

, which turns southward to the spillway. The river runs generally south and passes through Iowa City

Iowa City, Iowa

Iowa City is a city in Johnson County, State of Iowa. As of the 2010 Census, the city had a total population of about 67,862, making it the sixth-largest city in the state. Iowa City is the county seat of Johnson County and home to the University of Iowa...

 and the University of Iowa

University of Iowa

The University of Iowa is a public state-supported research university located in Iowa City, Iowa, United States. It is the oldest public university in the state. The university is organized into eleven colleges granting undergraduate, graduate, and professional degrees...

 campus. A lowhead dam at Burlington Street in Iowa City is the last dam before the river's confluence with the Mississippi. South of Iowa City, it is joined by the English River

English River (Iowa)

The English River is a tributary of the Iowa River in southeastern Iowa in the United States. The main stem of the river is long. Including its longest headwaters tributary, the North English River, the total length increases to . Via the Iowa River, it is part of the Mississippi River...

, and then in Louisa County

Louisa County, Iowa

-2010 census:The 2010 census recorded a population of 11,387 in the county, with a population density of . There were 5,002 housing units, of which 4,346 were occupied.-2000 census:...

 it is joined by the Cedar River to flow into the Mississippi.

The Iowa River is noted for recreational and commercial fishing. Game fish include largemouth

Largemouth bass

The largemouth bass is a species of black bass in the sunfish family native to North America . It is also known as widemouth bass, bigmouth, black bass, bucketmouth, Potter's fish, Florida bass, Florida largemouth, green bass, green trout, linesides, Oswego bass, southern largemouth...

 and smallmouth bass

Smallmouth bass

The smallmouth bass is a species of freshwater fish in the sunfish family of the order Perciformes. It is the type species of its genus...

, walleye

Walleye

Walleye is a freshwater perciform fish native to most of Canada and to the northern United States. It is a North American close relative of the European pikeperch...

, northern pike

Northern Pike

The northern pike , is a species of carnivorous fish of the genus Esox...

, channel

Channel catfish

Channel catfish, Ictalurus punctatus, is North America's most numerous catfish species. It is the official fish of Missouri, Iowa, Nebraska, Kansas, and Tennessee, and is informally referred to as a "channel cat". In the United States they are the most fished catfish species with approximately 8...

 and flathead catfish

Flathead catfish

The flathead catfish , also called the yellow cat, opelousas, and shovelhead cat, are large North American freshwater catfish. This is the only species of the genus Pylodictis...

, crappie

Crappie

Crappie is a genus of freshwater fish in the sunfish family of order Perciformes. The type species is P. annularis, the white crappie...

 and other panfish

Panfish

A panfish, also spelled pan-fish or pan fish, is an edible game fish that usually doesn't outgrow the size of a frying pan. The term is also commonly used by anglers to refer to any small catch that will fit in a pan, but is large enough to be legal. However its definition and usage varies with...

. The Coralville Reservoir is commercially fished

Commercial fishing

Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...

 for carp

Carp

Carp are various species of oily freshwater fish of the family Cyprinidae, a very large group of fish native to Europe and Asia. The cypriniformes are traditionally grouped with the Characiformes, Siluriformes and Gymnotiformes to create the superorder Ostariophysi, since these groups have certain...

 and buffalo fish

Ictiobus

Ictiobus, also known as Buffalo fish, is a genus of freshwater fish common in the United States. It is sometimes mistaken for carp because of its flat face and large, silver scales running along the body, though it lacks the whisker-like mouth appendages common to carp...

.

Pine Lake State Park

Pine Lake State Park

Pine Lake State Park is a state park of Iowa, USA. The park comprises encompassing two lakes: Lower Pine Lake and Upper Pine Lake. The park is located near Eldora and Steamboat Rock.-Camping:...

 is located on the Iowa River at Eldora

Eldora, Iowa

Eldora is a city in Hardin County, Iowa, United States. The population was 3,035 at the 2000 census. It is the county seat of Hardin County. Eldora is located adjacent to the Iowa River and Pine Lake State Park. The city is most famous for the filming of the 1996 movie Twister on location. The...

.

Floods

The Iowa can flood, notably in the June 2008 Midwest floods

June 2008 Midwest floods

The June 2008 Midwestern United States floods were flooding events which affected portions of the Midwest United States. After months of heavy precipitation, a number of rivers overflowed their banks for several weeks at a time and broke through levees at numerous locations. Flooding continued...

, and the Great Flood of 1993

Great Flood of 1993

The Great Mississippi and Missouri Rivers Flood of 1993 occurred in the American Midwest, along the Mississippi and Missouri rivers and their tributaries, from April to October 1993. The flood was among the most costly and devastating to ever occur in the United States, with $15 billion in damages...

. The Cedar and its tributaries, including the Shell Rock River

Shell Rock River

The Shell Rock River is a tributary of the Cedar River in southern Minnesota and northern Iowa in the United States. Via the Cedar and Iowa rivers, it is part of the watershed of the Mississippi River. The United States Board on Geographic Names settled on "Shell Rock River" as the stream's name...

, can contribute to flooding events.