Sources: NElmC
- Samuel L. Clemens to Arthur Locker, 17 September 1872 · London, England · UCCL00808
- Samuel L. Clemens to John T. Lewis, 24 August 1877 · Elmira, N.Y. · 2nd of 2 · UCCL13815
- SLC to Sidney B. and Isabel S. Howell, 22 March 1880 · Hartford, Connecticut · UCCL13033
- Samuel L. Clemens to Julia Jones Beecher, 30 May 1880 · Hartford, Conn · UCCL01809
- SLC to Unidentified, April 1883 · Hartford, Conn · UCCL11286
- SLC to Frank B. Darby, 10 January 1886 · Hartford, Conn · UCCL09083
- SLC to Francis Wayland, 15 January 1886 · Hartford, Conn · UCCL09951
- SLC to Elisha M. Van Aken, 7 September 1887 · Elmira, N.Y · UCCL11519
- SLC per Franklin G. Whitmore to Secty C. Harry Eaton and American Water Color Society, 9 February 1890 · Hartford, Conn · UCCL08935
- SLC to Joseph Hatton, 15 November 1890 · Hartford, Conn · UCCL04114
- SLC to ? Moscovitz, 31 December 1893 · New York, N.Y · UCCL04547
- SLC to Julia J. Beecher, 2 July 1895 · Elmira, N.Y · UCCL04923
- SLC to Unidentified, 23 May 1899 · Vienna, Austria · UCCL09361
- SLC to Unidentified, 5 July 1899 · London, England · UCCL05650
- SLC to Unidentified, November 1899 · London, England · UCCL11288
- SLC to Miss O'Reilly, 27 August 1901. Saranac Lake, New York · UCCL13274
- SLC to Helene Elisabeth Picard, 21 April 1902 · Riverdale, N.Y · UCCL06327
- SLC to Susan L. Crane, 3 January 1903 · Riverdale, N.Y · UCCL11399
- SLC to Charles J. Langdon, 15 October 1904 · New York, New York · UCCL13025
- SLC to Susan L. Crane, 21 February 1905 · New York, N.Y · UCCL12418
- SLC to Margaret Shaw Graham, December 1905 · New York, N.Y · UCCL10374
- SLC to Unidentified, 6 December 1905 · New York, N.Y · UCCL12419
- SLC to Maud W. Littleton, 31 December 1907 · New York, N.Y · UCCL11931
- SLC to Martin W. Littleton, 6 December 1908 · Redding, Conn · UCCL08171
- SLC to Maud W. Littleton, 3 February 1909 · Redding, Conn · UCCL11932
- SLC to Maud W. Littleton, 11 March 1909 · Redding, Conn · UCCL11933
- SLC to Harriet A. Rathbone, 29 December 1909 · Redding, Conn · UCCL08528
- SLC to Maud W. Littleton, 12 March 1910 · Hamilton, Bermuda · UCCL11934
- SLC to Elisha M. Van Aken, 8 October n.y. · Hartford, Conn · UCCL11521
- SLC to Unidentified, Unknown date · Unknown place · UCCL12425
- SLC to Unidentified, Unknown date · Unknown place · UCCL12424
- SLC to Unidentified, Unknown date · Unknown place · UCCL12423
- SLC to Unidentified, Unknown date · Unknown place · UCCL12422
- SLC to Unidentified, Unknown date · Unknown place · UCCL12421
- SLC to ? Wetter, Unknown date, New York, N.Y · UCCL03218
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