Illinois State Route 161 is a east-west highway across Northern St. Clair County. This is one of the main highway through the Greater-Belleville Area. IL St Rt 161 passes through the following towns in St. Clair County. Fairview Heights
Belleville
Swansea
Mascoutah
New Baden
IL St Rt 161 is multi-plexed in St. Clair County. Illinois State Route 158, near Scott Air Force Base. IL St Rt 161 intersects the following highways in St. Clair County. Illinois State Route 159, in Belleville.
The western end point in Fairview Heights. WB IL St Rt 161 in Fairview Heights. A BGS on WB IL St Rt 161. EB IL St Rt 161 east of IL St Rt 159. WB IL St Rt 161 on Sherman in Belleville. WB IL St Rt 161 on the eastside of Belleville. A BGS on SB IL St Rt 158. A junction marker on SB IL St Rt 158/EB IL St Rt 161. A St. Clair County mile marker. EB IL St Rt 161 in New Baden.