From their History page:
The vision of a national digital library has been circulating among librarians, scholars, educators, and private industry representatives since the early 1990s. Efforts led by a range of organizations, including the Library of Congress, HathiTrust, and the Internet Archive, have successfully built resources that provide books, images, historic records, and audiovisual materials to anyone with Internet access. Many universities, public libraries, and other public-spirited organizations have digitized materials, but these digital collections often exist in silos. The DPLA brings these different viewpoints, experiences, and collections together in a single platform and portal, providing open and coherent access to our society’s digitized cultural heritage.
The DPLA planning process began in October 2010 at a meeting in Cambridge, MA. During this meeting, 40 leaders from libraries, foundations, academia, and technology projects agreed to work together to create “an open, distributed network of comprehensive online resources that would draw on the nation’s living heritage from libraries, universities, archives, and museums in order to educate, inform, and empower everyone in current and future generations.”
See the website here: