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, memoranda, receipts, certificates, financial and legal documents, envelopes, clippings, pamphlets, and other printed materials dealing with social and family relationships, the sons' education, professions, and military careers, the Mexican-American War and the Civil War, real estate and financial matters, and with the deaths and bequests of various family members. Among the cataloged correspondents are: Alexander Hamilton, John Church Hamilton, Gen. Schuyler Hamilton, Ralph Isaacs Ingersoll, Charles Augustus Peabody, Gen. J. Fred Pierson, Gen. Winfield Scott, Martin Van Buren, and a manuscript by George Washington.