The Clark mss., 1909-1957, consists of the letters and writings of author, editor, and publisher Thomas Curtis Clark, 1877-1953, as well as the autographs and poems of other writers collected by him.
The Colorado-Sinclair mss. consists of letters exchanged between author, Upton Beall Sinclair, 1878-1968, and University of Colorado Director of Libraries Eugene Holt Wilson, 1909-?, Boulder, Colorado, August 25-October 31, 1950.
