HathiTrust reached a major milestone on January 5, 2012, exceeding 10 million volumes in its digital collections. More than 2.7 million of these volumes are in the public domain. Read more about the breakdown of collections by copyright distribution date, volume distribution by date and language, and see a timeline of growth:

http://www.hathitrust.org/blogs/perspectives-from-hathitrust/ten-million-and-counting