In Illinois, how property is valued and taxed seems pretty obscure, and may involve witchcraft.

The rate on my tax bill is 6.03%. But that's on a "net taxable value" that's about 40% of what I paid for the place 15 years ago, and maybe 25% of what I could get for the place now. So the rate is effectively 2.5% of what I paid, or 1.4% of what I could get. The total tax has also gone up 26% since 2020, increasing by more each year, but I don't know whether they've raised the rate each year or the valuation.

It's probably possible to find out how it works, but there's not much point. It is what it is, so you pay it or leave. No one lives in Illinois for the tax rates.