In 1940, these letters were given by Gilbert's son, Archibald Marvine Gilbert, to the American Geographical Society. In October 1978, the letters were in the custody of Irvil P. Schultz, then head of the U.S. Geological Survey Denver Library, who deposited them in the Field Records Library in 1980. NO-7704. Two expandable envelopes with: letter dated February 14, 1940, signed by Archibald Marvine Gilbert; also, 86 additional letters, most from individuals, congratulating G.K. Gilbert on his upcoming 75th birthday, May 6, 1918. G.K. Gilbert died May 1, 1918. Correspondents (names as signed): Geo. H. Ashley; Henry M. Ami (2 letters); Mrs. G.T. Backus; H. Foster Bain; Joseph Barrell; Willet G. Miller, Cyril W. Knight and Alfred G. Burrows - the three signed one letter; George F. Becker; William Bowie; John C. Branner; Florence Bascom; John P. Buwalda; T.C. Chamberlin; F.W. Clarke; William H. Dall; N.H. Darton; W.M. Davis; Arthur L. Day; Davis T. Day; J.S. Diller; B.K. Emerson; H.L. Fairchild; Nevin M. Fenneman; R.W. Gannett; Herbert E. Gregory; John F. Hayford; Henry W. Henshaw; W.F. Hillebrand; William H. Hobbs; W.H. Holmes; E.C. Hutchinson; J.S. Hutchinson; Lincoln Hutchinson; Joseph P. Iddings. Also, Arthur Keith; J.F. Kemp; Mrs. J.F. Kemp; F.H. Knowlton; S.J. Kubel; Andrew Lawson; Joseph N. LeConte; M.O. Leighton; Frank Leverett; Waldemar Lindgren; George D. Louderback; Hiram Dryer McCaskey; John D. McChesney; I.R. Marshall; R.B. Marshall; C.F. Marvin; Edward B. Matthews; W.C. Mendenhall; George P. Merrill; E.E. Murphy; F.H. Newell; Edmond O'Neill; Henry Fairfield Osborn; Louis V. Pirrson; Raphael Pumpelly; Frederick Leslie Ransome; Richard Rathbun; Harry Fielding Reid; John H. Renshawe; Wm. North Rice; H.C. Rizer; Henry H. Robinson; Charles Schuchert; W.B. Scott; H. M. Smith; Arthur C. Spence. Also, J.E. Spurr; J.J. Stevenson; George W. Stose; Frank B. Taylor; James E. Talmage; Rush Rhees and Charles Hoenig - signed same letter; Henry W. Turner; Charles R. VanHise; T. Wayland Vaughan; Charles D. Walcott; W.W. Watts; Bailey Willis; Robert S. Woodward; Charles G. Yale; Faculty Club of the University of California - multiple signatures.