The papers comprise correspondence, documents, institutional files, writings, lectures, memoirs, research notes, photographs, third party materials, printed materials, periodicals, microfilms, audio material, and digital files accrued by historian and professor emeritus of Columbia University, Leopold H. Haimson, during his professional life.

The collection includes correspondence, photographs, manuscripts and printed materials. There are letters from Ekaterina Kuskova (Mrs. S.N. Prokopovich) and photographs of Mark Aldanov, Marie Curie, Aleksandra Kollontaĭ, Ekaterina Kuskova, Pavel Mili︠u︡kov, Mikhail Osorgin, Sergeĭ Prokopovich and Nadezhda Teffi among others. The manuscripts include drafts and typescripts for several dozen articles and chapters as well as untitled manuscripts and notes. The printed materials contain clippings and offprints of articles by Prokopovich, periodicals he edited, and copies of his major books.