Northwestern Illinois books digitized

From Illinois Harvest. Be advised that their search engine is wacky in that it doesn't respect quotation marks, so any search involving the word "county" will generate thousands of irrelevant hits. My best results come from searching all or most of a book's title. I'll see if I can spare you this nonsense by including the permanent URLs for each book.

Portrait and biographical album of Rock Island County, Illinois (Chicago: Biographical Publishing Company, 1885)

Past and present of Rock Island County, Ill., containing a history of the county (Chicago: H.F. Kett, ~1877)

Early Rock Island, by William A. Meese (Moline: Press of Desaulniers & Co., 1905). "I have aimed to collect all data and facts relating to this country up to and including the year 1832."

Historic Rock Island County (Rock Island: Kramer & Co., 1908)

Official Book of the Fort Armstrong centennial celebration, June 18th-24th, 1916
by the Rock Island County Historical Society and the Historical Section of the Davenport [Iowa] Academy of Sciences (Rock Island: E. O. Vaile, Jr., 1916)

and, moving south a bit:

History of Mercer County: together with biographical matter, . . . by Mercer County Historical Society (Chicago: H.H. Hill & Co., 1882) 912 pp.

History of Mercer and Henderson Counties, by Mercer County Historical Society (Chicago: H.H. Hill & Co., 1882) 1414 pp.

You don't have to be the genealogical equivalent of a rocket scientist to discover that these two books contain a lot of overlapping content. But they can't be identical with one being 50% longer than the other, can they?