Selling a US property -- how to prove I own it?

I need to sell a property in IL but in all the years and moves I have lost the documentation that proves I own it in the first place.  Does anyone have any ideas of how I can address this?

Should be public record.  Contact the local county or city offices.

All deeds will have been recorded in the county/city records. Big question - assuming you are in a property tax state, who has been paying? That also s/be the owner of record.