Illinois Route 100

Illinois Route 100 (IL-100) is a 159.09-mile-long (256.03 km) state highway in the southwest Illinois. It generally parallels the Illinois River. Starting in downtown Alton, it trends northward to Buckheart Township near Canton. It makes up much of the Illinois River Road, a U.S. National Scenic Byway.[1]

Illinois Route 100
Route information
Maintained by IDOT
Length159.09 mi[1] (256.03 km)
Major junctions
South end US 67 in Alton
  I-72 / US 36 in Bluffs
US 67 in Meredosia
US 67 / IL 103 in Frederick
US 24 / US 136 in Lewistown
North end IL 78 in Dunfermline
CountiesMadison, Jersey, Greene, Calhoun, Pike, Scott, Morgan, Cass, Schuyler, Fulton
Highway system
IL 99IL 101

Route description

The southern end in Alton is at US 67 where Broadway, Landmarks, and Piasa Streets come together. It follows the east bank of the Mississippi River and Illinois River through Grafton until Hardin, where it crosses the Joe Page Bridge across the Illinois River. A portion of the Great River Road was on an old railroad alignment, which you can see parts of just north of Alton. During periods of high water, this highway is susceptible to flooding.

North of Hardin, the highway follows the west bank of the Illinois River until the bridge near Florence. From that point on, IL 100 follows mostly farmland on much higher ground until Beardstown, where it will cross the river a third and final time. It will again follow the west bank of the Illinois River until US 136. After meeting with US 24 in Duncan Mills, IL 100 and US 24 is cosigned until Lewistown. North of Lewistown, IL 100 heads in a north-east alignment until its northern terminus with IL 78 near Dunfermline.

Illinois River Road

Illinois Route 100 overlaps the Illinois River Road from Grafton to Detroit.


IL 100 originally went from Godfrey from the intersection at Godfrey Road and Homer M. Adams Parkway (IL 111/US 67) to Grafton on the current IL 3. In 1987, IL 3, 143, and 100 alignments were changed to their current routes in the River Bend (Illinois) area when the Homer M. Adams Parkway Extension was opened. On June 28, 2012, the Florence Bridge over the Illinois River was closed for at least 9 months by IDot due to difficulties with the lifting mechanism that allows barge traffic to pass under the bridge. Inspections suggested that continued use of the lift span could harm the structural integrity of the bridge. As barges need to pass under the bridge, the lifting span was raised up and the bridge was closed. Motorists wishing to cross the river must use the signed detour utilizing Illinois Route 106, US Route 54, and Interstate 72/US Route 36. The bridge was repaired and reopened to traffic on April 22, 2013, only to be closed again for seven days of repairs after a barge collision on June 20, 2019.

Major intersections

MadisonAlton0.000.00 US 67 (Piasa Street) Godfrey, St. LouisSouthern terminus
JerseyGrafton15.124.3 IL 3 south (North Market Street)Northern terminus of IL 3
Richwood Township30.749.4 IL 16 east JerseyvilleSouthern end of IL 16 concurrency
CalhounHardin36.658.9 IL 16 endsNorthern end of IL 16 concurrency; western terminus of IL 16
Kampsville46.274.4 IL 96 north QuincySouthern terminus of IL 96
46.574.8 IL 108 east (Marquette Street) Carrollton, CarlinvilleWestern terminus of IL 108
PikeDetroit71.3114.7 IL 106 west (Main Street) PittsfieldWestern end of IL 106 concurrency
Scott76.9123.8 IL 106 east WinchesterEastern end of IL 106 concurrency
80.8130.0 I-72 / US 36 Springfield, QuincyI-72 exit 46; diamond interchange
Morgan91.1146.6 US 67 south / IL 104 east JacksonvilleSouthern end of US 67/IL 104 concurrency
92.0148.1 IL 104 west Meredosia, QuincyNorthern end of IL 104 concurrency
CassBeardstown105.4169.6 IL 125 east SpringfieldWestern terminus of IL 125
Schuyler107.4172.8 US 67 north / IL 103 west Rushville, Mt. SterlingNorthern end of US 67 concurrency; eastern terminus of IL 103
FultonIsabel Township135.5218.1 US 136 east HavanaEastern end of US 136 concurrency
138.2222.4 US 24 west RushvilleSouthern end of US 24 concurrency
140.4226.0 US 136 west MacombWestern end of US 136 concurrency
Lewistown145.1233.5 US 24 east / IL 97 south (East Avenue East) PeoriaNorthern end of US 24 concurrency; southern end of IL 97 concurrency
146.5235.8 IL 97 north CubaNorthern end of IL 97 concurrency
Dunfermline159.09256.03 IL 78 Canton, HavanaNorthern terminus
1.000 mi = 1.609 km; 1.000 km = 0.621 mi


  1. Illinois Technology Transfer Center (2006). "T2 GIS Data". Retrieved 2007-11-08.
  2. Carlson, Rich. Illinois Highways Page: Routes 81 thru 100. Last updated March 15, 2005. Retrieved April 20, 2006.
  3. Google (February 26, 2017). "Overview Map of IL 100" (Map). Google Maps. Google. Retrieved February 26, 2017.
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