Illinois Route 159
|Maintained by IDOT|
|Length||64.90 mi (104.45 km)|
|Existed||1926 – present|
|South end||IL 3 / IL 154 in Red Bud|
| US 50 / I-64 in Fairview Heights
US 40 / I-55 / I-70 in Collinsville
I-270 in Glen Carbon
|North end||IL 16 in Royal Lakes|
|Counties||Randolph, Monroe, St. Clair, Madison, Macoupin|
Illinois Route 159 is a north–south state road in southwestern Illinois. Its southern terminus is at Illinois Route 3 and Illinois Route 154 in Red Bud and its northern terminus at Illinois Route 16 in Royal Lakes. This is a distance of 64.90 miles (104.45 km).
Widening of a stretch of Illinois 159 to five lanes took place around 2006; the highway is now five lanes from Fairview Heights to Edwardsville, with the exception of downtown Collinsville, where a similar widening project was completed in 2012.
SBI Route 159 ran from Red Bud to Alton. In 1964, the Edwardsville to Alton segment was changed to Illinois Route 143, and Illinois 159 was run north through Edwardsville to Royal Lakes, replacing Illinois Route 112. This created an unusual 3 way multiplex in downtown Edwardsville where you went north on 157, south on 159, and east on 143 for 2 blocks. This multiplex was not signed, however. In 2003 Illinois 159 was rerouted through Edwardsville, which eliminated that multiplex.
An Alternate Illinois Route 159 was proposed by Edwardsville on the old Illinois 159 alignment on Troy Road, but was never implemented.
|Randolph||Red Bud||0.0||0.0||IL 3 / IL 154 / Great River Road (Market Street, Main Street)|
|Monroe||Hecker||6.6||10.6||IL 156 west (Monroe Street)||South end of IL 156 overlap|
|St. Clair||||7.8||12.6||IL 156 east||North end of IL 156 overlap|
|Belleville||20.2||32.5||IL 15 – East St. Louis, Mt. Vernon|
|20.5||33.0||IL 13 / IL 158 (South Belt)|
|Swansea||22.7||36.5||IL 161 (North Belt)|
|Fairview Heights||27.2||43.8||I-64 (US 50) – Mt. Vernon, St. Louis|
|Madison||Collinsville||35.3||56.8||I-55 / I-70 (US 40) – Chicago, St. Louis|
|Glen Carbon||38.6||62.1||I-270 – Effingham, St. Charles|
|Edwardsville||42.6||68.6||IL 143 east / IL 157 (Vandalia Street)||South end of IL 143 overlap|
|43.9||70.7||IL 143 west (Edwardsville Road)||North end of IL 143 overlap|
|Macoupin||||61.7||99.3||IL 138 east|
|Royal Lakes||64.9||104.4||IL 16|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi