The Illinois River is a principal tributary of the Mississippi River and is approximately 273 miles (439 km) long. Located in the U.S. state of Illinois, the river has a drainage basin of 28,756.6 square miles (74,479 km²). The Illinois River begins with the confluence of the Des Plaines and Kankakee rivers in the Chicago metropolitan area, and it generally flows to the southwest across Illinois, until it empties into the Mississippi near Grafton, Illinois. Its drainage basin extends into southeastern Wisconsin, northwestern Indiana, and a very small area of southwestern Michigan in addition to central Illinois. Along its shores are several river ports, including Peoria, Illinois. Historic recreation areas on the river include Starved Rock and the internationally important wetlands of the Emiquon Complex and Dixon Waterfowl Refuge.