The main body of the collection consists of Kellogg's personal incoming and outgoing correspondence with fellow zoologists and geologists regarding research in zoology and marine geologic formations. A significant amount of correspondence with institutions also exists, notably with the Bureau of Biological Survey, the Carnegie Institution of Washington, and the National Research Council. For other institutional correspondence, material may be found with that of specific individuals in the employ of an institution. The remainder of the collection consists of a personal information file; a collection of photographs documenting exhibit openings, Smithsonian staff retirement functions, and Kellogg's membership in various organizations; and divisional histories of the National Museum of Natural History prepared for the Smithsonian Centennial.
Correspondents include: Clinton G. Abbott, Othenio Abel, Charles Christopher Adams, Theodor G. Ahrens, Glover Morrill Allen, American Society of Mammalogists, Copley Amory, Rudolph Martin Anderson, Harold Elmer Anthony, Arctic Research Laboratory Advisory Board, Merle Fowler Bancroft, Thomas Barbour, F. J. F. Barrington, Seth Bertram Benson, Fritz Berckhemer, Edward Wilber Berry, Edward Willard Berry, Clarence Birdseye, Else Bostelmann, Karl Brandt, James C. Brash, Barnum Brown, William Alanson Bryan, Charles Dean Bunker, Bureau of Biological Survey, William Henry Burt, Angel Cabrera, Charles L. Camp, Leonard Carmichael, Carnegie Institution of Washington, Clifford N. Carver, Ermine Cowles Case, E. Burnham Chamberlain, Bruce Lawrence Clark, Robert Ervin Coker, Charles Wythe Cooke, Harold J. Coolidge, Jr., Ira E. Cornwall, Luther Sheeleigh Cressman, Giorgio Dal Piaz, Pirie Davidson, William B. Davis, Herbert Girton Deignan, A. B. Van Deinse, Donald Ryder Dickey, W. O. Dietrich, Alban T. A. Dobson, Abraham Lincoln Dryden, Emmett Reid Dunn, Lucius R. Eastman, Maxim Kondradovich Elias, Robert Kendall Enders, William Louis Engels, Barton Warren Evermann, Francis Charles Fraser, Eustace L. Furlong, Eugene Maximilian Karl Geiling, Charles W. Gilmore, Raymond Maurice Gilmore, Walter Granger, Madison Grant, William King Gregory, Robert Fiske Griggs, Joseph Grinnell, Melville Bell Grosvenor, Herman Gunter, Eugene Raymond Hall, William John Hamilton, Jr., G. Dallas Hanna, Sidney Frederic Harmer, Francis Harper, Robert Torrens Hatt, Curtis J. Hesse, F. Gilbert Hindsdale, Arthur T. Hopwood, William Temple Hornaday, Edgar Billings Howard, Alfred Brazier Howell, International Whaling Commission, David Starr Jordon, Journal of Mammalogy, Theodor Just, A. Remington Kellogg, Henry Higgins Lane, Frederic Augustus Lucas, Marcus Ward Lyon, Jr., Alfredo Augusto de Oliveira Machado e Costa, William D. Matthew, C. Hart Merriam, Charles Warren Merriam, John Campbell Merriam, Franklin Metcalf, Gerrit Smith Miller, Jr., Roy L. Moodie, Charles Morrice, Robert Cushman Murphy, National Academy of Sciences, National Research Council, Gladwyn Kingsley Noble, Walter Collins O'Kane, Henry Fairfield Osborn, Wilfred Hudson Osgood, A. P. Ousdal, Earl Leroy Packard, Evgenii Nikanorovich Pavlovsky, John Charles Phillips, Edward Alexander Preble, Sydney Prentice, Henry Cushier Raven, Alfred S. Romer, Carlos Rusconi, Wilford Edwin Sanderson, Hurbert G. Schneck, George Gaylord Simpson, Earle Sloan, Hans Winge Sorensen, Herman Augustus Spoehr, Eberhard Stechow, Henryk Bronislaw Stenzel, Ruben Arthur Stirton, Chester Stock, George Linius Streeter, Ernst Stromer Von Reichenbach, J. Magruder Sullivan, Edward H. Taylor, Charles Haskins Townsend, T. Wayland Vaughan, Charles D. Walcott, Lewis Hill Weed, Alexander Wetmore, George Bernays Wislocki, Howard I. Wordell.