Illinois State Highway System

State Highway System
State Highway System
	Highway markers for Interstate 57, U.S. Route 45, Illinois Route 1 and the Chicago Skyway
	Overall map of system: freeways in light blue, tollways in green, other highways in yellow
System information
	Maintained by IDOT, ISTHA, and SCC
Formed	November 5, 1918
Highway names
Interstates	Interstate X (I-X)
US Highways	U.S. Route X (US X)
State	Illinois Route X (IL X)
System links
	Illinois State Highway System; Interstate; US; State; Tollways; Scenic;

The organized State Highway System of the U.S. state of Illinois comprises all of the state routes in the state.

^ Carlson, Miriam C. (April 2002). "Out of the Mud: Illinois' Good Roads Movement". Illinois History. 55 (3). Illinois Historic Preservation Agency: 47–9. ISSN 0019-2058 – via Illinois Periodicals Online.