Illinois Route 100

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Illinois Route 100

IL 100 highlighted in red
Route information
Maintained by IDOT
Length159.09 mi[1] (256.03 km)
Major junctions
South end US 67 in Alton
Major intersections I-72 / US 36 in Bluffs
US 67 / IL 104 in Meredosia
US 67 / IL 103 in Frederick
US 24 / US 136 in Lewistown
North end IL 78 in Dunfermline
CountryUnited States
CountiesMadison, Jersey, Greene, Calhoun, Pike, Scott, Morgan, Cass, Schuyler, Fulton
Highway system
IL 99 IL 101

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]

Route description

Southern end of IL 100 and IL 16 concurrence

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.

IL 100 along the Great River Road

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

US 67 (Piasa Street) / Great River Road south – Godfrey, St. Louis
Southern terminus
IL 3 south (North Market Street) / Illinois River Road
Northern terminus of IL 3; Illinois River Road begins at junction
Richwood Township30.749.4
IL 16 east – Jerseyville
Southern end of IL 16 concurrency
IL 16 ends
Northern end of IL 16 concurrency; western terminus of IL 16

IL 96 north / Great River Road / Great River Road Spur begins – Quincy
Southern terminus of IL 96; northern end of Great River Road concurrency

IL 108 east (Marquette Street) / Great River Road Spur – Carrollton, Carlinville
Western terminus of IL 108; northern end of Great River Road Spur concurrency
IL 106 west (Main Street) – Pittsfield
Western end of IL 106 concurrency
IL 106 east – Winchester
Eastern end of IL 106 concurrency
80.8130.0 I-72 / US 36 – Springfield, QuincyI-72 exit 46; diamond interchange

US 67 south / IL 104 east – Jacksonville
Southern end of US 67/IL 104 concurrency
IL 104 west – Meredosia, Quincy
Northern end of IL 104 concurrency
IL 125 east – Springfield
Western terminus of IL 125

US 67 north / IL 103 west – Rushville, Mt. Sterling
Northern end of US 67 concurrency; eastern terminus of IL 103
FultonIsabel Township135.5218.1
US 136 east / Illinois River Road north – Havana
Eastern end of US 136 concurrency
US 24 west – Rushville
Southern end of US 24 concurrency
US 136 west – Macomb
Western end of US 136 concurrency

US 24 east / IL 97 south (East Avenue East) – Peoria
Northern end of US 24 concurrency; southern end of IL 97 concurrency
IL 97 north – Cuba
Northern 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. ^ a b 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.

External links