Correspondence, manuscripts of poems, and manuscripts of lectures by Benjamin. The correspondence consists of original letters of Benjamin, typescript and photostatic copies of Benjamin letters in other libraries, and letters to Benjamin from some of his literary contemporaries including Paul Hamilton Hayne, Willis Gaylord Clark, John Lothrop Motley, and Fitz-Greene Halleck. Many of the letters relate to Park Benjamin's lecture tours. There are other family letters and many documents relating to the Benjamin family,and two letterbooks of John Lothrop Motley. Also, a large amount of genealogical material of the Benjamin family, and its related families from the 16th century to the present day. There are also financial records, monographs, clippings, and photographs.

1992-1995 Additions: 138 volumes of his diaries, 1920-1994, have been added, as well as 12 letters from W.A. Craigie concerning new entries for the Oxford English Dictionary, 1 drawing in the style of John Leech, 2 19th century drawings, the manuscript of his "Young John of Gaunt; a poem in fourteen cantos", 22 engraved American portraits, 5 maps of the American Civil and Revolutionary Wars, 3 scrapbooks, World War I to 1976, his commonplace book, 1927-1990, several of his published books, and "The Sheriff's Prisoner", an autobiographical account of his 8 months in Brixton Prison for Obscene Libel on the publication of "Guido and the Girls", along with letters and documents re. this case.