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.

Papers of the Jay family and of those families related to the Jay family, including Bruen, Butterworth, Chapman, Clarkson, Dawson, Du Bois, Field, Iselin, McVickar, Mortimer, O'Kill, Pellew, Pierrepont, Prime, Robinson, Schieffelin, Von Schweinitz, Sedgwick, and Wurts. In addition to family and personal matters, the correspondence deals with anti-slavery, New York State civil service, repeal of the Missouri Compromise, the Civil War, the Blair Bill, international affairs, and New York City and State politics and government. There are letters from numerous prominent persons including George Bancroft, F.A.P. Barnard, Bismarck, William Cullen Bryant, Aaron Burr, James Fenimore Cooper, Ralph Waldo Emerson, Hamilton Fish, Albert Gallatin, Horace Greeley, Nathaniel Hawthorne, Oliver Wendell Holmes, Washington Irving, Frances Anne Kemble, Jenny Lind, Henry W. Longfellow, Seth Low, James Russell Lowell, John Stuart Mill, Alice Duer Miller, Clement Clarke Moore, J.P. Morgan, Thomas Nast, Commodore Matthew Perry, Franklin D. Roosevelt, Theodore Roosevelt, Elihu Root, Carl Schurz, William H. Seward, William T. Sherman, Charles Sumner, and John Greenleaf Whittier.