Approximately 12,000 letters to Allan Nevins from various correspondents including James Truslow Adams, Franklin Delano Roosevelt, Harry S. Truman, Willa Cather, Frances Folsom Cleveland, Van Wyck Brooks, Robert Frost, Newton D. Baker, Archibald MacLeish, John D. Rockefeller, Jr., Carl Sandburg, and Henry Wallace; notes and typescripts for Nevins' books including Emergence of Lincoln, The Ordeal of Democracy, Rockefeller, and History and Historians, with notes by editor Ray A. Billington; miscellaneous transcripts, clippings, newspapers, and photographs. Also, autograph letters and manuscripts by presidents, Civil War figures, financiers, politicians, and authors. There are also the Brand Whitlock World War I Diaries and letters to him by such people as Herbert Hoover, Gen. John J. Pershing, and others.

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.