Sources: MiD
- Samuel L. Clemens to Edward H. Paige, 20? May 1870 · Buffalo, N.Y · UCCL11699 MiD
- Samuel L. Clemens to James Redpath, 31 December 1873 · London, England · UCCL01023 MiD
- SLC to Henry Lee, 1 January–7 January 1874 · London, England · UCCL09693 MiD
- Samuel L. Clemens to Thomas Bailey Aldrich, 20 October 1875 · Hartford, Conn · UCCL01274 MiD
- Samuel L. Clemens to George S. Merrill, per Fanny C. Hesse, 8 February 1877 · Hartford, Conn · UCCL04140 MiD
- SLC to Edward F. Noyes, 26 February 1881 · Hartford, Conn · UCCL01916 MiD
- SLC to Karl Gerhardt and Hattie J. Gerhardt, 7 May 1883 · Hartford, Conn · UCCL02379 MiD
- SLC to Karl Gerhardt, 11 September 1884 · Elmira, N.Y · UCCL04135 MiD
- SLC to Karl Gerhardt, 28 September 1884 · Hartford, Conn · UCCL01443 MiD, MB
- SLC to Karl Gerhardt, 21 August 1886 · Unknown place · UCCL04265 MiD
- SLC per Olivia L. Clemens to Unidentified, 25 June 1895 · Elmira, N.Y · UCCL04901 MiD
- SLC to Gilbert Burgess, 3 March 1897 · London, England · UCCL05182 MiD
- SLC to Sigmund Schlesinger, 20 October 1898 · Vienna, Austria · UCCL05452 MiD
- SLC to Clara L. Clemens, 18 March 1902 · Miami, Fla · UCCL06306 MiD
- SLC to Nathaniel S. Olds, 21 April 1902 · Riverdale, N.Y · UCCL06326 MiD
- SLC to ? Van Dreele, 22 July 1904 · Lee, Mass · UCCL06898 MiD
- SLC to Ralph W. Ashcroft, 24 October 1904 · New York, N.Y · UCCL06933 MiD
- SLC to John Y. MacAlister, 22 November 1904 · New York, N.Y · UCCL06953 MiD
- William L. Bryan to SLC, 29 March 1907 · Bloomington, Ind. · UCLC36281 MiD
- SLC per Isabel V. Lyon to William L. Bryan, 29 March 1907 · New York, N.Y · UCCL07679 MiD
- SLC to Clara L. Clemens, 12 July 1907 · London, England · UCCL07783 CLjC, MiD
- SLC to Clara L. Clemens, 5 April 1908 · Hamilton, Bermuda · UCCL07969 MiD
- SLC to Jean Clemens, 8 February 1909 · Redding, Conn · UCCL08342 MiD
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