I've recently published the Handbook of Old Gallatin County and Southeastern Illinois. It contains a reprint of the 1887 history of Gallatin County, plus two new sections on from other 19th and early 20th Century sources on the county detailing Early Anecdotes about the county as well as its Military History. The fourth section contains more than 250 biographies from a number of sources. It also contains a full index.
For more information check out www.IllinoisHistory.com/Handbook.