The HathiTrust.org is a partnership of major research institutions and libraries working to ensure that the cultural record is preserved and accessible long into the future. There are more than 100 partners in HathiTrust, and membership is open to institutions worldwide.The website currently hosts more than 13 million total volumes with over 5 million in the public domain. Genealogists will find this a treasure trove of information from surname books to local and state histories. The Digital Public Library of America currently has over 10 million items from libraries, archives, and museums. The DPLA is dedicated to providing this content free to the entire country.
Quoting from the blog post entitled, "DPLA and HathiTrust Partnership Supports Open E-Book Programs."
The Digital Public Library of America and HathiTrust have had a strong relationship since DPLA’s inception in 2013. As part of our ongoing collaboration to host and make digitized books widely available, we are now working to see how we can provide our services to exciting new initiatives that bring ebooks to everyone.
The Humanities Open Book grant program, a joint initiative of the National Endowment for the Humanities and the Andrew W. Mellon Foundation, is exactly the kind of program we wish to support, and we stand ready to do so. Under this funding program, NEH and Mellon will award grants to publishers to identify previously published books and acquire the appropriate rights to produce an open access e-book edition available under a Creative Commons license. Participants in the program must deposit an EPUB version of the book in a trusted preservation service to ensure future access.
HathiTrust and DPLA together offer a preservation and access service solution for these re-released titles. Since 2013 public domain and open access titles in HathiTrust have been made available through the Digital Public Library of America. HathiTrust recently added its 5 millionth open e-book volume to its collection, and as a result DPLA now includes over 2.3 million unique e-book titles digitized by HathiTrust’s partner institutions, providing readers with improved ability to find and read these works. Materials added to the HathiTrust collections can be made available to users with print disabilities, and they become part of the corpus of materials available for computational research at the HathiTrust Research Center. By serving as a DPLA content hub, HathiTrust can ensure that open access e-books are immediately discoverable through DPLA.The basic idea here is to make books that would otherwise be unavailable online due to copyright or other issues and make them available to the public through the DPLA and the HathiTrust.