Beinecke Rare Book and Manuscript Library at Yale University

The Beinecke Rare Book & Manuscript Library is one of the world's largest libraries devoted entirely to rare books and manuscripts and is Yale's principal repository for literary archives, early manuscripts, and rare books. The Beinecke Library's robust collections are used to create new scholarship by researchers from around the world. 

Source: http://beinecke.library.yale.edu/