The Mark Twain Papers contain the private papers of Samuel Langhorne Clemens (Mark Twain) that he himself segregated and made available to his official biographer, Albert Bigelow Paine. From Paine's death in 1937 until 1979, they were under the care of four successive editors who were also literary executors for Clemens's estate: Bernard DeVoto at the Houghton Library of Harvard University, Dixon Wecter at the Henry E. Huntington Library in San Marino, California, and later here at Berkeley, followed in turn by Henry Nash Smith and Frederick Anderson, both at Berkeley. This basic core of original documents by and about Mark Twain was deposited at Berkeley in 1949 and bequeathed to the University of California upon the death in 1962 of Mark Twain's sole surviving daughter, Clara Clemens Samossoud. Since 1949 the Library has added, and continues to add, original documents to that basic core: letters, manuscripts, a dozen scrapbooks kept by Clemens and his brother Orion, first editions and other rare printings, photographs, and various important collateral documents, such as the diaries of Mark Twain's secretary, Isabel V. Lyon. Since 1980 the expanding archive and the editorial project based in it have been under the direction of Robert H. Hirst.
As a result of intensive, ongoing editorial work since the mid 1960s, and with the cooperation of hundreds of institutions and individuals around the world, a working archive of photocopies and transcriptions has also been assembledchiefly of letters by Clemens, his wife, and three daughters, but also letters to them, all the major literary manuscripts (published and unpublished) that are known to survive, books from his personal library, photographs, drawings, and so forth.
This combination of original and photocopied documents now makes it possible to read virtually every document in Mark Twain's hand known to survive, without ever leaving Berkeley: some 50 notebooks kept by Clemens between 1855 and his death in 1910; approximately 11,000 letters by him or his immediate family, and more than 17,000 letters to them; about 600 literary manuscripts left unpublished (and often unfinished) in his lifetime; manuscripts ranging from mere fragments to complete drafts (including chapters Clemens later deleted) for almost all of the books he published and for perhaps a tenth of his published short works (sketches, essays, editorials, speeches, poems); working notes, typescripts, and proofs for various titles; first editions and other lifetime editions, including American, English, Australian, Canadian, and German or Continental printings of his various books; about 150 books from his library, usually with marginalia; uncounted business documents, clippings, scrapbooks, interviews, bills, checks, photographs, and a handful of objects originally owned by him.