The Illinois Daughters of the National Society Of The Daughters Of The American Revolution has an Illinois library. This DAR library is housed at the Brehm Library at Mt. Vernon, IL. I do not have a complete list of their holdings. Some of the things you will find there are: The DAR lineage books. The patriot indexes. Family histories. History books. Census film. The many volume's of the New England Historical & Genealogical Society books. Don't let this little gem go un-noticed when searching the southern Illinois area. These are just a few books, they in fact take the whole south wall and several feet of the west wall of the room and as high as you can reach. There is I would guess, at least one book for every state in the union.
While your at Brehm, look at their microfiche collection. They also have drawers full of film for Revolutionary and 1812 War pension applications. There is an index to these rolls of film. It is called "Index Of Revolutionary War Pension Applications In The National Archives. If you are trying to prove a revolutionary war soldier, this is the place to go.
Brehm is a part of the Shawnee Library System. Their main genealogy collection was previously housed at Carterville. The NSDAR collection was previously housed at Centralia.