The journals of the Illinois State Historical Society are digitized and available on line. That presently includes all issues from 1950 through 2006.
The collection is not really searchable...you are just able to browse each issue. When you finally get down to an article of interest to you, it downloads as a pdf file.
As one reviewer said: there is genealogical gold here!
You can browse the collection at: http://dig.lib.niu.edu/ISHS/index.html