The Illinois River begins south of Joliet near Interstate 55 and heads west through Morris, Marseilles, Ottawa and La Salle. West of Lasalle, near the Lake DePue Conservation Area (CA), the river begins to head south into Peoria, then southwest to just below Beardstown and finally south again emptying into the Mississippi River at Grafton.
The river gives rise to a multitude of recreational areas, including Goose Lake Prarie State Natural Area, William G. Stratton State Park, Gebhard Woods State Park, Illini State Park, Buffalo Rock State Park & Effigy Tumili, Starved Rock State Park, Matthiesen State Park and Spring Lake State Park.
