Starved Rock State Park in the context of LaSalle County, Illinois

The Illinois River (Miami-Illinois: Inoka Siipiiwi) is a principal tributary of the Mississippi River at approximately 273 miles (439 km) in length. Located in the U.S. state of Illinois, the river has a drainage basin of 28,756.6 square miles (74,479 km). 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 banks are several river ports, including the largest, Peoria, Illinois. Historic and recreation areas on the river include Starved Rock, and the internationally important wetlands of the Emiquon Complex and Dixon Waterfowl Refuge.

The river was important among Native Americans and French traders as the principal water route connecting the Great Lakes with the Mississippi. The French colonial settlements along these rivers formed the heart of the area known as the Illinois Country in the 17th and 18th centuries. After the construction of the Illinois and Michigan Canal and the Hennepin Canal in the 19th century, the role of the river as link between Lake Michigan and the Mississippi was extended into the era of modern industrial shipping. The Illinois now forms the basis for the Illinois Waterway, extending the river's capabilities for navigation and commercial shipping.

The Kankakee Torrent was a catastrophic flood that occurred about 19,000 calibrated years ago in the Midwestern United States. It resulted from a breach of moraines forming a large glacial lake fed by the melting of the Late Wisconsin Laurentide Ice Sheet. The point of origin of the flood was Lake Chicago. The landscape south of Chicago still shows the effects of the torrent, particularly at Kankakee River State Park and on the Illinois River at Starved Rock State Park.

La Salle or LaSalle is a city in LaSalle County, Illinois, United States, located at the intersection of Interstates 39 and 80. It is part of the Ottawa, IL Micropolitan Statistical Area. Originally platted in 1837 over one square mile (2.6 square kilometers), the city's boundaries have grown to 12 sq mi (31 km). Named in honor of 17th century Illinois valley explorer, the Sieur de La Salle, city boundaries extend from the Illinois River and Illinois and Michigan Canal to a mile north of Interstate 80 and from the city of Peru on the west to the village of North Utica on the east. Starved Rock State Park is located approximately 5 mi (8 km) to the east. The population was 9,582 as of the 2020 census, down from 9,609 at the 2010 census. LaSalle and its twin city, Peru, make up the core of the Illinois Valley. Due to their combined dominance of the zinc processing industry in the early 1900s, they were collectively nicknamed "Zinc City."