Incoming correspondence (1856-1904); letterpress copybooks (1868-1901); legal and financial (including real estate) records (1797-1901); amd personal papers (1862-1901). Notable among the real estate records are documents relating to the furnishing and household expenses of Huntington's San Francisco residence, and records relating to the design, construction, decoration, furnishing, and maintenance of Huntington's palatial home on 57th St. in New York City. Correspondents include Oakes Ames, Susan B. Anthony, S.C. Armstrong, Samuel B. Axtell, James G. Blaine, William B. Bonn, Marcus D. Boruck, John Boyd, Luigi di Cesnola, William E. Chandler, David Colton, John Conness, Charles Crocker, Charles F. Crocker, E.B. Crocker, John Echols, J.H. Flagg, Francis W. Fox, Richard Franchot, Isaac E. Gates, F.N. Gilman, George C. Gorham, Jay Gould, Ulysses S. Grant, Mark Hopkins, Anna Judah, Edwin H. Miller, William H. Mills, L. Bradford Prince, A.A. Sargent, Charles H. Sherrill, Jane and Leland Stanford, William M. Stewart, James Storrs, William B. Strong, Alban N. Towne, Booker T. Washington, W.C. Wickham, George W. Williams, and J.H. Woodward. Some of Huntington's correspondence was conducted through the use of cipher systems and many letters provide word keys to substitution codes. Cipher telegrams are often accompanied by translations.