The Sinclair mss. IV, 1900-1963, consists of correspondence, writings, and monetary statements of author Upton Beall Sinclair, 1878-1968, and of his wife, Mary Craig (Kimbrough) Sinclair, 1883-1961.
The Trotskii mss., 1900-1957, consist principally of the correspondence of Lev Trotskii, 1879-1940, Russian communist leader, and Max Eastman, 1883-1969, author, during the period when Eastman was preparing his book about Trotskii in 1922 and 1923 and later when he served unofficially as Trotskii's literary agent from 1929 to 1933.
The Rogers, H.M. mss., 1895-1930, consist of letters from Booth Tarkington, 1869-1946, author, to Herbert Milton Rogers, 1870?-1931, lawyer, of Omaha, Nebraska, and former classmate of Tarkington at Princeton University.
The Overstreet mss., 1894-1985, consist of the correspondence, writings, lecture material, and memorabilia of married couple Harry Allen Overstreet and Bonaro Wilkinson Oversteet, who together wrote a bestselling book on Communism.
The Eastman mss. IV, 1890-2009, consist of the photographs, correspondence, personal papers, writings, and artwork of Max Eastman, 1883-1969; Yvette Szekely Eastman, 1912-2014; and Eliena Krylenko Eastman, 1895-1956.
The Amfiteatrov mss., 1890-1948, consists of the correspondence and writings of journalist and playwright Aleksandr Valentinovich Amfiteatrov, 1862-1938.