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 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 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. 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.