Cook County uses a property tax assessment equalization factor near 2. They under-assess the value of your home and property. While you think this saves you, it doesn't. Your property is worth more, but you can't get more because the County assesses it low.

Hop into the Chicagoland suburbs, and the tax assessment equalization factor ranges from 1 to 1.5. In Lake County, they over-assess the value of your home and property. You then have to go through a lengthy bureaucratic appeal process full of red-tape to try to lower your assessment. I'd say you have a 1 in 8 chance of winning the appeal.

It helps when good old e3NiNe there went to high-school with one of the people who work in the township assessor's office

State income tax is separate from state/county/local sales taxes.