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.