The collection contains correspondence with the authors, including contracts signed with authors as well as negotiations with the authors over various aspects of publishing their works; financial records documenting many aspects of the operation of Harper & Brothers, including royalties paid to authors, records of stock offerings and company reorganizations, and general ledgers which contain daily notes on all aspects of the operation of the business; book catalogues and trade lists; research materials collected by Eugene Exman for his history of Harper & Brothers; visual materials, from drawings and photographs of Harper's authors to colophon designs and an oil painting of the original Harper's building.

Letters and manuscripts of English and American authors collected by Gilvarry. Included are a letter from Arnold Bennett, London, 1923, to Miss Renard; a poem "The Sea Bird to the Wave" by Padraic Colum, 1916; an essay of D.H. Lawrence, 1926?; a letter from Ezra Pound, London, ca. 1914, to Seumas O'Sullivan; a letter from George Santayana, Rome, 1927, to E.W. Titus; and a photograph with signature of Herman Melville, New York, 1885.