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.

Cotton's 15 nonconsecutive manuscript pocket diaries for the period from 1850 to 1877. The diaries outline his life and travels. The entries for the Civil War years are especially interesting. He often describes the capital's fear of enemy invasion, recent nearby incursions, troop movements, and the general preoccupation with all aspects of the war. He called on President Lincoln, attended his second inauguration, and notes the passage of the Emancipation Proclamation. He describes the capital's joyous mood at the fall of Richmond and the gloom over the assassination of Lincoln. He attended the military court to see the conspirators. Later volumes talk about Pension Bureau affairs and his health and that of his family.

Proofs, photographs, photostatic copies, and other printed materials of Roscoe. Included are proofs and illustrative materials for his book The Web Of Conspiracy; The Complete Story Of The Men Who Murdered Abraham Lincoln, and a printed copy of his book, Only In New England, a book of crime fiction.