Correspondence, manuscripts, subject files and research notes of Sigmund Diamond. Included among the correspondence are Diamond's letters to and from various distinguished members of Columbia University and other academic insitutions, as well as correspondence with many noted sociologists and historians. Included in the manuscripts is Diamond's "In Quest." The subject files comprise material from Diamond's tenure at Columbia and include some material pertaining to his forced departure from Harvard in the 1950's due to his previous communist affiliation, and his active role in maintaining the efficacy of the Freedom of Information Act. The research files include microfilms and notes.