Illinois Route 21

Illinois Route 21 (IL 21) is an arterial northsouth state highway in northeastern Illinois. It runs from Illinois Route 43 (Harlem Avenue) in Niles to U.S. Route 41 (Skokie Highway) north of Gurnee. Illinois 21 is 28.13 miles (45.27 km) long.[1]

Illinois Route 21
Milwaukee Avenue
Riverside Drive
IL 21 highlighted in red
Route information
Maintained by IDOT
Length28.13 mi[1] (45.27 km)
ExistedNovember 5, 1918[2]–present
Major junctions
South end IL 43 in Niles
  US 14 in Niles
US 45 in Prospect Heights
US 45 in Lincolnshire

I-94 in Gurnee
North end US 41 in Gurnee
CountiesCook, Lake
Highway system
US 20IL 22

Along most of its length, Illinois 21 is called Milwaukee Avenue. North of Gurnee, it is called Riverside Drive.

Route description

Illinois 21 was the principal route to Milwaukee, Wisconsin before the construction of both the Skokie Highway and the Tri-State Tollway (Interstate 94 and Interstate 294). The towns of Glenview, Libertyville, and Gurnee are principally located along this road. It follows the Des Plaines River for its entire length, and overlaps U.S. Route 45 between Lincolnshire and Prospect Heights.

South of Illinois 43, Milwaukee Avenue remains a major arterial road until it reaches the downtown area of Chicago, where its historical terminus at Lake Street has been moved back to Grand Avenue. It is one of the few diagonal streets in the grid street layout of Chicago.


SBI Route 21 ran from Chicago to Antioch along Milwaukee Avenue and current Illinois Routes 43, 83 and 137. In Chicago, it also ran along Elston Avenue. In 1940, the route was moved to a new route to Grayslake, and then continued to Antioch. In 1963, Illinois 21 was dropped entirely from Grayslake to Antioch, and in 1972, it was shortened further to its current southern terminus at Illinois 43. The next year, Illinois 21 was rerouted to Gurnee. Illinois 83 and 137 replaced the old Route 21 to (and through) Grayslake.[2]

Major intersections

CookNiles0.00.0 IL 43 (Harlem Avenue)
1.93.1 US 14 (Dempster Street)Grade-separated interchange
3.04.8 IL 58 (Golf Road)
Prospect Heights7.311.7 US 45 south (Des Plaines River Road)South end of US 45 overlap
Willow Road, Palatine Road to I-294
Grade-separated interchange
Wheeling10.016.1 IL 68 (Dundee Road)
county line
11.017.7Lake Cook RoadGrade-separated interchange
LakeLincolnshire14.222.9 IL 22 (Half Day Road)
14.523.3 US 45 northNorth end of US 45 overlap
Vernon Hills17.227.7 IL 60 (Town Line Road)
Libertyville20.232.5 IL 176 (Park Avenue)
21.835.1 IL 137 (Peterson Road, Buckley Road)
Gurnee24.739.8 IL 120 (Belvidere Road)Grade-separated interchange
I-94 west (Tri-State Tollway) Wisconsin
No access from or to I-94 east; I-94 exit 10
27.043.5 IL 132 (Grand Avenue)
28.1345.27 US 41 (Skokie Highway)
1.000 mi = 1.609 km; 1.000 km = 0.621 mi


  1. Illinois Technology Transfer Center. T2 GIS Data. Retrieved April 7, 2006. As documented in Wikipedia:WikiProject U.S. Roads/Lengths/Illinois.
  2. Carlson, Rick. Illinois State Highways: Routes 21 through 40. Last updated March 15, 2006. Retrieved March 22, 2006.
  3. Google Maps,

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