^Westbound trailblazer leading away from the interchange with Illinois 251 in Rockford, February 2024.
US Route 20 enters Illinois in the northwest corner of the state to become the northernmost east-west highway in northwest Illinois, then it turns a bit more southeasterly toward Chicago once it passes through the Rockford area. It connects Dubuque, Iowa, to Galena, Freeport, Rockford, and Belvidere, before becoming more diagonal to reach places like Elgin, LaGrange, and Chicago. It uses US Routes 45 and 12 to flank around the western and southern sides of downtown Chicago, crossing into Indiana very near Lake Michigan.
US Route 20 enters Illinois crossing the Mississippi River out of Dubuque, Iowa...
US Route 20 enters Illinois crossing the Mississippi River out of Dubuque, Iowa...
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Fresh off the Mississippi River bridge, US Route 20 meets a sort of interchange with Illinois 35 in East Dubuque:
Before reaching Galena, US Route 20 is joined by Illinois 84 which comes from the north:
US Route 20 and Illinois 84 continue through Galena together, and about ten miles past Galena, Illinois 84 splits away to go south...
In Stockton, Illinois, US Route 20 is joined by Illinois 78 which comes from the south...
The concurrency shared by US Route 20 and Illinois 78 lasts a little over the mile, then Illinois 78 splits away to head north:
At Lena, US Route 20 crosses Illinois 73:
US Route 20 then departs from the Freeport area, and a series of ramps accesses the east end of the business alignment of US Route 20. For eastbound traffic on US Route 20, this is signed as an exit to Springfield Road, which reaches the business route:
After passing the town of Winnebago, US Route 20 creates a second business alignment heading east into inner Rockford...
South of downtown Rockford, the main freeway bypass of US Route 20 has a diamond interchange with Illinois 2...
The US Route 20 then crosses the Rock River to encounter a cloverleaf interchange with Illinois 251...
At a directional interchange, US Route 20 is joined by Interstate 39, which approaches from the south...
The next interchange is a cloverleaf where US Route 20 leaves the freeway carrying Interstate 39 to continue east on a surface road:
At Belvidere, US Route 20 meets the east end of the business alignment of US Route 20, just south of the end of Illinois 76:
In Marengo, US Route 20 crosses Illinois 23, south of the western end of Illinois 176:
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US Route 20 turns more southeasterly here, and it dives south of Interstate 90, where an interchange connects the two highways...
At Starks, US Route 20 joins Illinois 47 south at a point where Illinois 72 comes from the east to also join Illinois 47 south:
A short triplicate of routes is formed, but it soon ends as US Route 20 turns east off of Illinois 47 as Illinois 72 turns westerly:
In Elgin, US Route 20 becomes an old bypass freeway with narrow clearances, and it meets Illinois 31 at a diamond interchange...
As the freeway continues through Elgin, US Route 20 accesses Illinois 25 via a series of dangerous tight ramps with slow curve speeds...
At a slightly modified fountain interchange, US Route 20 accesses Illinois 59...
US Route 20 is a surface road at this point, but in Hanover Park, an interchange accesses the western end of Illinois 390:
In Addison, US Route 20 meets one of the northernmost interchanges of Interstate 355:
A block farther east, US Route 20 crosses Illinois 53:
US Route 20 then acts as the surface road at a folded diamond interchange with Illinois 83, where Addison meets Elmhurst:
After traveling about another mile, US Route 20 joins Interstate 290 east:
At a very strange interchange near Northlake, US Route 20 splits from Interstate 290 to access Illinois 64 in the same direction, but US Route 20 immediately splits from Illinois 64 to head southeasterly on its own...
At this same interchange, US Route 20 meets a ramp to/from Interstate 294's northern direction:
Entering Westchester, the combination of US Routes 12, 20, and 45 meet an interchange with Interstate 290's east-west section:
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At Hodgkins, the trio of US Routes including US Route 20 meets a cloverleaf interchange with Interstate 55:
After that, US Routes 12, 20, and 45 cross the Des Plaines River and meet a full-access interchange with Illinois 171, passing under Interstate 294 with (almost) no access:
Near Hickory Hills, US Route 20 finally splits from US Route 45 to head east along 95th Street, but US Route 12 also makes the turn onto 95th Street...
US Route 20 stays concurrent with US Route 12 heading east, and the two routes meet a full-access interchange with Interstate 294...
Soon after that, US Routes 20 and 12 meet a cloverleaf interchange with Illinois 43 near Chicago Ridge...
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At Oak Lawn, US Routes 20 and 12 cross Illinois 50...
Having entered the south side of Chicago, US Route 12 and US Route 20 meet an interchange with Interstate 94...
The end of US Route 12's stint in Illinois is the point where US Routes 12, 20, and 41 cross into Indiana together, about 1000 feet from the Lake Michigan, and underneath Interstate 90. An assortment of scattered ramps provide full access to and from Interstate 90, where the Chicago Skyway becomes the western end of the Indiana Toll Road.
