Illinois State Route 21 runs north-south through the center of Lake County. The name that this highway carries for it's life it Milwaukee Ave. IL St Rt 21 passes through the following towns in Lake County. Buffalo Grove Riverwoods
Lincolnshire Vernon Hills Libertyville
IL St Rt 21 is multi-plexed in Lake County. U.S. Rt. 45, from the Lake/Cook County Line to Lincolshire.