Correspondence (including family letters dating from 1814), diaries, letter books, notebooks, notes and memoranda, charts, tables, reports, articles, memorabilia, landscape sketches, blueprints, maps, and miscellaneous printed matter. Chief interest centers in Becker's professional papers covering his long service as Geologist-in-Charge, U. S. Geological Survey, during which time he conducted investigations in Nevada, southern Alaska, South Africa, the Pacific slope, and the Philippines. Other papers concern his service as geophysicist of the Carnegie Institution, 1898, as U. S. representative at the Radioactivity Congress in Brussels, 1910, and as president of the Geological Society of America, 1914. Correspondents include Andreas Arzruni, James F. Bell, Theodore E. Burton, William Crozier, Edward S. Dana, James D. Dana, Samuel F. Emmons, Archibald Geikie, Arnold Hague, Eugene W. Hilgard, Edmund O. Hovey, Henry M. Howe, Louis Janin, Waldemar Lindgren, Charles W. Merrill, Simon Newcomb, Charles S. Peirce, Chester W. Purington, Theodore Roosevelt, Henry W. Turner, Charles D. Walcott, and Robert S. Woodward. Indexed in part. Includes a list of Becker's notes and unpublished MSS.