R.”, a “Robber Baron” and “the Greatest Bookdealer in the World”.Rosenbach is credited with popularizing the collecting of American literature at a time when only European literature was considered collectible.
He also advanced the idea of book collecting as a means of investment and published several articles and books to increase interest in rare books and manuscripts.
He bought and sold numerous items throughout his life, including eight Gutenberg Bibles, more than 30 Shakespeare's First Folio, a copy of the Bay Psalm Book and the manuscripts of Ulysses and Alice's Adventures in Wonderland.
The life-time total of his purchases is estimated to be worth more than $75,000,000 in 2019.His philanthropic contributions include donating his collection of children's books to the Free Library of Philadelphia, establishing the Rosenbach Fellowship in Bibliography at the University of Pennsylvania and willing his estate to the Rosenbach Foundation, which established the Rosenbach Museum & Library.