Sources: Axelrod
- Samuel L. Clemens to Henry Abbey, 21 August 1869 · Buffalo, N.Y · UCCL00337
- Samuel L. Clemens to Elisha Bliss, Jr., 28 December 1869 · New York, N. Y · UCCL00396
- Samuel L. Clemens to James Redpath, 9 October 1870 · Buffalo, N.Y · UCCL10496
- Samuel L. Clemens to Elisha Bliss, Jr., 26 October 1870 · Buffalo, N.Y · UCCL00514
- Samuel L. Clemens to Elisha Bliss, Jr., 24 January 1871 · Buffalo, N.Y · UCCL00562
- Samuel L. Clemens to Fannie Dennis, 17 February 1871 · Buffalo, N.Y · UCCL00578
- Samuel L. Clemens to James Redpath, 27 June 1871 · 2nd of 2 · Elmira, N.Y · UCCL00623
- Samuel L. Clemens to James Redpath, 27 June 1871 · 1st of 2 · Elmira, N.Y · UCCL00621
- Samuel L. Clemens to James Redpath, 19 July 1871 · Elmira, N.Y · UCCL10497
- Samuel L. Clemens to James Redpath, 22 September 1871 · Buffalo, N.Y · UCCL10498
- Samuel L. Clemens to James Redpath, 24 October 1871 · Washington, D.C · UCCL00666
- Samuel L. Clemens to James Redpath, 7 January 1872 · Wooster, Ohio · UCCL00710
- Samuel L. Clemens to Henry Lee, 4 October 1872 · London, England · UCCL00818
- Samuel L. Clemens to Unidentified, 18 October 1872 · London, England · UCCL11320
- Samuel L. Clemens to Henry Lee, 5 November 1872 · London, England · UCCL11069
- Samuel L. Clemens to James Gordon Bennett, Jr., 17 November 1875 · Hartford, Conn · UCCL10499
- Samuel L. Clemens to William Dean Howells, 1 January 1876 · Hartford, Conn · UCCL00849
- Samuel L. Clemens to William Wright (Dan De Quille), 7 March 1876 · Hartford, Conn · UCCL01312
- Samuel L. Clemens to William Wright (Dan De Quille), 26 March 1876 · Hartford, Conn · UCCL01318
- Samuel L. Clemens to Andrew Chatto, 25 April 1879 · Paris, France · UCCL01650
- Samuel L. Clemens to H. L. Joachimsen · 8 April 1880 · Hartford, Conn · UCCL10562
- Samuel L. Clemens to Unidentified, 21 May 1880 · Hartford, Conn · UCCL11603
- Samuel L. Clemens to James R. Osgood, 19 October 1880 · Hartford, Conn · UCCL10668
- Samuel L. Clemens to James R. Osgood, 16 December 1880 · Hartford, Conn · UCCL01873
- SLC to Stephen C. Massett, 7 October 1881 · Hartford, Conn · UCCL02047
- SLC to James R. Osgood, 24 October 1881 · Hartford, Conn · UCCL02061
- SLC to Unidentified, 19 February 1882 · Hartford, Conn · UCCL02160
- SLC to James R. Osgood, 11 June 1882 · Hartford, Conn · UCCL08975
- SLC to R. Christie, 4 July 1882 · Hartford, Conn · UCCL11608
- SLC to Unidentified, 19 December 1883 · Hartford, Conn · UCCL11346
- SLC to Charles R. Deacon and Clover Club, 3 January 1884 · Hartford, Conn · UCCL09948
- SLC to Unidentified, 14 January 1884 · Hartford, Conn · UCCL02575
- SLC to Josiah H. Gilbert, 25 February 1884 · Hartford, Conn · UCCL10563
- SLC to Lorenz Rohr, 12 May 1884 · Hartford, Conn · UCCL02975
- SLC to James B. Pond, 1 September 1884 · Elmira, N.Y · UCCL01446
- SLC to Henry C. Robinson, 15 September–16 September 1884 · Elmira, N.Y · UCCL11234
- SLC to Neil Burgess, 28 October 1884 · Hartford, Conn · UCCL10564
- SLC to Lou W. Benjamin, 10 April 1886 · Hartford, Conn · UCCL03382
- SLC to Edward W. Lummis, 17 May 1886 · Hartford, Conn · UCCL10561
- SLC to Frederick J. Hall, 3 September 1886 · Elmira, N.Y · UCCL03451
- SLC to William Smith, 18 October 1886 · Hartford, Conn · UCCL03462
- SLC to George Parsons Lathrop, 12 July 1889 · Hartford, Conn · UCCL11168
- SLC to Katherine C. Bronson, 20 February 1893 · Florence, Italy · UCCL04341
- SLC to Susan L. Warner, 7 November 1893 · New York, N.Y · UCCL11607
- SLC to Clover Club, 3 January 1894 · New York, N.Y · UCCL12700
- SLC to Unidentified, 1 March 1894 · New York, N.Y · UCCL11609
- SLC to Edward Planta Nesbit, 13 October 1895 · Unknown place · UCCL10252
- SLC to J. Henry Harper, 7 October 1896 · London, England · UCCL05125
- SLC to J. Henry Harper, 27 October 1896 · London, England · UCCL05136
- SLC to Century editors, 30 August 1897 · Weggis, Switzerland · UCCL05282
- SLC to Robert Barr, 18 September 1897 · Weggis, Switzerland · UCCL10669
- SLC to Laura Rothmann, 30 September 1897 · Vienna, Austria · UCCL11063
- SLC to Walter Besant, 8 April 1898 · Vienna, Austria · UCCL03817
- SLC to Annette Hullah, 17 February 1899 · Vienna, Austria · UCCL11604
- SLC to Francis H. Skrine, 1 July 1899 · London, England · UCCL10569
- SLC to John Y. MacAlister, 28 September 1900 · London, England · UCCL05873
- Samuel L. Clemens to Unidentified, 16 November 1900 · New York, N.Y · UCCL13135
- SLC to Channing H. Cook, 19 November 1900 · Princeton, N.J · UCCL09774
- SLC to Unidentified, 10 January 1901 · New York, N.Y · UCCL10575
- SLC to Robert Reid, 21 January 1901 · New York, N.Y · UCCL10573
- SLC to William Winter, 8 December 1901 · Riverdale, N.Y · UCCL06185
- SLC to Chester S. Lord · 31 December 1901 · Riverdale, N.Y · UCCL06201
- SLC to Mr. Wolfe, 13 May 1902 · Riverdale, N.Y · UCCL06334
- SLC to Frederick W. Peabody, 4 April 1903 · Riverdale, N.Y · UCCL06613
- SLC to Franklin G. Whitmore, 11 April 1903 · Riverdale, N.Y · UCCL11602
- SLC to D. Stuckey Worthington, 10 March 1906 · New York, N.Y · UCCL07376
- SLC to Augusta (Lady) Gregory, 8 July 1907 · London, England · UCCL09401
- SLC to Margery H. Clinton, 2 December 1907 · New York, N.Y · UCCL07873
- SLC to Annie E. Trumbull, 8 December 1907 · New York, N.Y · UCCL11606
- SLC to Margery H. Clinton, 17 April 1908 · New York, N.Y · UCCL07979
- SLC to Clara L. Clemens, 22–23 October 1908 · Deal, N.J · UCCL04132
- SLC to Margery H. Clinton, 30 October 1908 · Redding, Conn · UCCL08150
- SLC to Zoheth S. Freeman, 16 November 1908 · Redding, Conn · UCCL08160
- SLC per Ralph W. Ashcroft to Unidentified, 4 March 1909 · Redding, Conn · UCCL11605
- SLC to Isabel S. Wayland, 29 September 1909 · Redding, Conn · UCCL10579
- SLC to William Henry Bishop, 13 October 1909 · Redding, Conn · UCCL11325
- SLC to Margery H. Clinton, 17 November 1909 · Redding, Conn · UCCL11244
- SLC to Unidentified, Unknown date · Unknown place · UCCL10571
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