The Chicago River is 156 miles long (251 km) and goes through the city of Chicago, Illinois, including the center of the city (the Chicago Loop). The river is not long, but it is known for being the reason why Chicago became an important place, as the connection between the Great Lakes and the Mississippi Valley waterways. The river is the only river in the world to be reversed (which is, made to flow backwards, in the opposite of its natural direction) by civil engineering.