I looked at the online marriage records. There is a Wilford but the marriage is for McDonough County November 17, 1864. You can view it at the Illinois State Archives site for online databases. Just search the Marriage Records database by putting in Mitchell, and you do need the comma after the last name. This will give you access to all the men named Mitchell in the State of Illinois prior to 1900 (some counties have put in later marriages if they had the info). You may find an approximate marriage date from 1920 or 1930 US census records. Joan in Illinois