River is a system of rivers and canals with a combined length of 156 miles (251 km) that runs through the city of the same name, including its center (the Chicago Loop). Though not especially long, the river is notable for being the reason why Chicago became an important location, as the link between the Great Lakes
and the Mississippi Valley waterways.
The source of the Main Stem of the Chicago River is Lake Michigan. Water enters the river through sluice gates at the Chicago River Controlling Works with a small additional flow provided by the passage of boats between the river and Lake Michigan through the Chicago Lock.