The Harris, L. mss. consists of materials related to the writing and publication of Upton Sinclair, American Rebel (Crowell, 1975), by author Leon A. Harris, 1926-2000.
The Howatt mss., 1902-1959, consist in the main of letters to David Howatt, 1882-1964 , farmer and secretary of Upton Beall Sinclair, from writers Harry Kemp, Upton Beall Sinclair, and William James Durant.
The Nikolaevskiî mss., 1938-1944, are letters and papers extracted from books collected by Boris Ivanovich Nikolaevskiî, 1887-1966, Russian revolutionary and author.
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 Sinclair mss. V, 1902, consists of the application of novelist Upton Beall Sinclair, 1878-1968, for a fellowship in the Graduate School of Harvard University for the year 1902-1903.
The Sinclair mss. VI, 1907-1977, consists of correspondence, writings, and miscellaneous papers by and relating to author Upton Beall Sinclair, 1878-1968, his wife Mary Craig (Kimbrough) Sinclair, 1882-1961, and his son David Sinclair, 1901-1987.
The Stokes mss., 1905-1906, consist primarily of letters from Upton Beall Sinclair, 1878-1968, novelist, to James Graham Phelps Stokes, 1872-1960, regarding the activities of the Intercollegiate Socialist Society.
The Toyoshima mss., 1966-1998, consists of audio cassette tapes of interviews conducted by Joe Toyoshima in 1966 as an oral history of Upton Sinclair. Also included are materials related to the Industrial Workers of the World.
The U.S. History mss., 1612-1977, consist of individual items acquired separately either as a gift, purchase, transfer, or removal from a variety of sources, relating to the United States. Additions continue to be made.