U.S. Route 20 in Illinois

U.S. Route 20 (US 20) in the state of Illinois is located in the northern region of the state. Running northwest to southeast, the highway enters the state in East Dubuque after crossing the Mississippi River and exits in the East Side neighborhood of Chicago. Within the state, US 20 is officially designated as the General Ulysses S. Grant Memorial Highway (often abbreviated as the Grant Memorial Highway), though this designation is primarily used west of Elgin.

West of the Chicago suburbs, the highway varies widely in configuration. While primarily a two-lane surface road connecting small towns and multiple north-south state highways, US 20 expands to two four-lane controlled-access freeways that bypass Freeport and Rockford; a similar configuration passes through Elgin. As it enters Cook County, US 20 becomes Lake Street, a multilane arterial surface road. Within the southwestern suburbs and the South Side, US 20 runs concurrently with US 12 and US 45 (later, joining US 41). On Indianapolis Boulevard, the shared US 12/US 20/US 41 exits Illinois as it passes underneath the Interstate 90 (I-90, Chicago Skyway) toll bridge.

Within Illinois, US 20 runs for a distance of 233.93 miles (376.47 km), its third-longest span east of the Mississippi River.