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.