Illinois property tax rate tops U.S., but pain worse in some areasIllinois property tax rate tops U.S., but pain worse in some areasIllinois' high property taxes hurt the economy, particularly in communities already struggling. Lake County’s effective property tax rate is 2.68%, but the average hides a huge disparity between communities in the far northeastern Illinois county. Lake Forest has a median home value of $909,800 and an effective property tax rate of 1.94%. St. Clair County in southwestern Illinois near St. Louis has an effective tax rate of 2.09%. East St. Louis’ median home value is $52,700 and residents face a 4.61% effective property tax rate.