Correspondence, manuscripts, notes, memoranda, notebooks, notecards, proofs, photographs, microfilms, and printed materials. The Papers include the manuscript research materials and correspondence for each of his books except his biography of Theodore Dreiser. Among the correspondents are William Benton, Bruce Catton, Carey McWilliams, Mrs. Fremont Older (Cora Miranda Baggerly Older), and Thornton Wilder.