The Biodiversity Heritage Library (BHL) is a consortium of natural history and botanical libraries that cooperate to digitize the legacy literature of biodiversity held in their collections and to make that literature available for open access and responsible use as a part of a global "biodiversity commons."
The University Library at the University of Illinois at Urbana Champaign is a participant (browse our contributions). Materials held in the former Biology and Natural History Survey Libraries have been digitized and contributed (see an example). BHL is particularly helpful in providing ready access to rare early biodiversity literature. Scientific names within works have been indexed and are searchable.
HathiTrust is a partnership of major research institutions and libraries working to ensure that the cultural record is preserved and accessible long into the future.
The University Library is a HathiTrust partner, and has recently made a strong push to digitize and release Illinois state documents in the University Library collection. Search the catalog for specific items, or search within full text of digitized items to find specific information. Materials not in copyright can be viewed/downloaded in their entirety. The HathiTrust Research Center helps researchers with text mining and other uses of HathiTrust content.