Rosenbach, a bibliophile and bookdealer of early Americana, Combined erudition with personal charm and the risk-taking instincts of a gambler, to rise to national prominence in the rare-book field. Dealing primarily in first and early editions of Americana and English literature, he acquired among his steady customers such millionaire collectors as Henry Huntington, Pierpont Morgan, Carl Pforzheimer, Lessing Rosenwald, Harry Widener, Edward S. Harkness, and Henry Folger, to whom he sold a first quarto edition of Shakespeare's plays in 1919 for $128,000, reputedly one of the highest prices ever paid for a rare book up to that time. From the 1920s on, Rosenbach Company was the acknowledged leader in the rare-book trade in the U.S. and hardly a major auction took place in which it did not successfully and often spectacularly bid.

2. Joshua Bloch, Editor, Journal of Jewish Bibliography: Volume 1 - c. 1980 reprint of 1938-39 first edition; Volume 2, #1-4, 1940, in original wrappers; Volume 3, # 1-3, 1942 in original wrappers. Lacking Volume 3 # 4 and Volume 4. All published.

Joshua Bloch was noted for being head of the Jewish Division of the New York Public Library, a post which he held from 1923 to 1956; under his direction the Library developed as one of the major collections of Judaica in the United States. Bloch arranged many major exhibitions of Judaica there. He published several major bibliography works based on his stay in the Library.