Sources: CtHSD
- SLC to Isabella Beecher Hooker, 24 January 1868 · Hartford, Conn · UCCL13620 CtHSD
- Samuel L. Clemens to Hattie Booth, 18 March 1870 · Buffalo, N.Y · UCCL00445 CtHSD
- Samuel L. Clemens to Jesse C. Haney, 14 November 1870 · Buffalo, N.Y · UCCL00534 CtHSD
- Olivia L. and Samuel L. Clemens to Alice Hooker Day, 25 January 1871 · Buffalo, N.Y · UCCL00564 CtHSD
- Samuel L. Clemens to Mary Mason Fairbanks, 6 November–10 December 1872 · London, England, or Hartford, Conn · UCCL11817 CtHSD
- Samuel L. Clemens to Henry Lee, 12 and 13 June 1873 · London, England · UCCL00924 CtHSD, NjBrun2
- Samuel L. Clemens to Edward T. Potter, 8 May 1874 · Elmira, N.Y · UCCL01086 CtHSD
- Samuel L. Clemens to John C. Day and Alice H. Day, 27 September 1876 · Hartford, Conn · UCCL01368 CtHSD
- Samuel L. and Olivia L. Clemens to the Saturday Morning Club, 25 March 1878 · Hartford, Conn · UCCL01549 CtHSD
- Samuel L. Clemens to the Saturday Morning Club, 1–11 June 1880 · Hartford, Conn · UCCL10480 CtHSD
- SLC to Laura Taft, 1 January 1883 · Hartford, Conn · UCCL11267 CtHSD
- SLC to Isabella B. Hooker, 27 May 1884 · Hartford, Conn · UCCL10482 CtHSD
- SLC to Elizabeth E. Jenkins, 2 October 1886 · Hartford, Conn · UCCL08836 CtHSD
- SLC to Elizabeth E. Jenkins, 20 October 1886 · Hartford, Conn · UCCL03472 CtHSD
- SLC to Harriet B. Stowe, 26 March 1887 · Hartford, Conn · UCCL11265 CtHSD
- SLC to Margaret Warner, 28 May 1887 · Hartford, Conn · UCCL11266 CtHSD
- SLC to John J. McCook, 8 November 1889 · Hartford, Conn · UCCL03962 CtHSD
- SLC to Mary M. Keller, 12 September 1890 · Tannersville, N.Y · UCCL04095 CtHSD
- SLC to OLC, 2 February 1894, 1st of 2 · New York, N.Y · UCCL14120 CtHSD
- SLC to Alice H. Day, 16 October 1894 · Rouen, France · UCCL04793 CtHSD
- SLC to George H. Keller, 25 November 1900 · New York, N.Y · UCCL05920 CtHSD
- SLC to Robert N. Stanley, 21 January 1901 · New York, N.Y · UCCL05973 CtHSD
- SLC to William Carey, 20 February 1901 · New York, N.Y · UCCL06006 CtHSD
- SLC to Mazie S. Robinson, 5 June 1901 · New York, N.Y · UCCL09793 CtHSD
- SLC to A. Schonstadt, 30 January 1902 · Riverdale, N.Y · UCCL10584 CtHSD
- SLC to William H. Gillette, 22 October 1903 · New York, N.Y · UCCL06751 CtHSD
- SLC to Unidentified, Unknown date · Unknown place · UCCL10583 CtHSD
- SLC to Richard Eugene Burton, Unknown date · Hartford, Conn · UCCL07433 CtHSD
- SLC to ? Dunham, Unknown date · Unknown place · UCCL07643 CtHSD
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