Materials related to the Mensheviks - one of the factions within the Russian socialist movement of the early 20th century, the other being the Bolsheviks. The factions emerged in 1903 following a dispute within the Russian Social Democratic Labour Party (RSDLP) between Julius Martov and Vladimir Lenin. The split proved to be long-standing and had to do both with pragmatic issues based in history, such as the failed revolution of 1905, and theoretical issues of class leadership, class alliances, and interpretations of historical materialism.
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.