Sources: CtHSD
- OLC to Alice H. Day, 25 December 1866 · New York, N.Y · UCCL10545
- OLC to Isabella B. Hooker, 7 April 1867 · Elmira, N.Y · UCCL09124
- OLC to Alice H. Day, 26 May 1867 · Elmira, N.Y · UCCL10543
- OLC to Alice H. Day, 7 June 1867 · Elmira, N.Y · UCCL10542
- OLC to Alice H. Day, 17 June 1867 · Elmira, N.Y · UCCL00138
- OLC to Alice H. Day, 29 July 1867 · Canandaigua, N.Y · UCCL10541
- OLC to Alice H. Day, 4 October 1867 · Elmira, N.Y · UCCL00150
- OLC to Alice H. Day, 30 October 1867 · Unknown place · UCCL10540
- OLC to Alice H. Day · UCCL00163
- SLC to Isabella Beecher Hooker, 24 January 1868 · Hartford, Conn · UCCL13620
- OLC to Alice H. Day · UCCL00193
- OLC to Alice H. Day, 8 March 1868 · Elmira, N.Y · UCCL10539
- OLC to Alice H. Day, 22 April 1868 · Elmira, N.Y · UCCL10538
- OLC to Alice H. Day, 8 August 1868 · Elmira, N.Y · UCCL10537
- OLC to Alice H. Day, 29 September 1868 · Elmira, N.Y · UCCL02754
- OLC to Alice H. Day, 5 November 1868 · Elmira, N.Y · UCCL10536
- OLC to Alice H. Day, 16 December 1868 · Elmira, N.Y · UCCL10535
- OLC to Alice H. Day · UCCL00308
- OLC to Alice H. Day · UCCL00370
- OLC to Alice H. Day · UCCL00409
- OLC to Alice Day Hooker · UCCL00444
- Samuel L. Clemens to Hattie Booth, 18 March 1870 · Buffalo, N.Y · UCCL00445
- OLC to Alice H. Day, May 1870 · Buffalo, N.Y · UCCL00474
- OLC to Alice H. Day, 6 June 1870 · Buffalo, N.Y · UCCL00477
- Samuel L. Clemens to Jesse C. Haney, 14 November 1870 · Buffalo, N.Y · UCCL00534
- Olivia L. and Samuel L. Clemens to Alice Hooker Day, 25 January 1871 · Buffalo, N.Y · UCCL00564
- Samuel L. Clemens to Mary Mason Fairbanks, 6 November–10 December 1872 · London, England, or Hartford, Conn · UCCL11817
- Samuel L. Clemens to Henry Lee, 12 and 13 June 1873 · London, England · UCCL00924
- OLC to Alice H. Day, 25 July 1873 · Edinburgh, Scotland · UCCL00776
- Samuel L. Clemens to Edward T. Potter, 8 May 1874 · Elmira, N.Y · UCCL01086
- Samuel L. Clemens to John C. Day and Alice H. Day, 27 September 1876 · Hartford, Conn · UCCL01368
- OLC to Annie E. Trumbull, Unknown date · Unknown place · UCCL09056
- Samuel L. and Olivia L. Clemens to the Saturday Morning Club, 25 March 1878 · Hartford, Conn · UCCL01549
- Samuel L. Clemens to the Saturday Morning Club, 1–11 June 1880 · Hartford, Conn · UCCL10480
- OLC to Alice H. Day, 30 August 1882 · Elmira, N.Y · UCCL10530
- OLC to George H. Warner, 17 November 1882 · Hartford, Conn · UCCL10608
- SLC to Laura Taft, 1 January 1883 · Hartford, Conn · UCCL11267
- OLC to Alice H. Day and John C. Day, 7 January 1884 · Hartford, Conn · UCCL10529
- SLC to Isabella B. Hooker, 27 May 1884 · Hartford, Conn · UCCL10482
- Susy (Olivia Susan) Clemens to Mary Foote, May 1886 · Hartford, Conn · UCCL03397
- Susy (Olivia Susan) Clemens to Mary Foote, May 1886 · Hartford, Conn · UCCL03396
- Susy (Olivia Susan) Clemens to Mary Foote, 15 May 1886 · Hartford, Conn · UCCL03400
- SLC to Elizabeth E. Jenkins, 2 October 1886 · Hartford, Conn · UCCL08836
- SLC to Elizabeth E. Jenkins, 20 October 1886 · Hartford, Conn · UCCL03472
- SLC to Harriet B. Stowe, 26 March 1887 · Hartford, Conn · UCCL11265
- SLC to Margaret Warner, 28 May 1887 · Hartford, Conn · UCCL11266
- OLC to Alice H. Day, 25 December 1888 · Hartford, Conn · UCCL10603
- SLC to John J. McCook, 8 November 1889 · Hartford, Conn · UCCL03962
- OLC to Laura Dunham, 19 December 1889 · Hartford, Conn · UCCL03990
- OLC to Alice H. Day, 11 April 1890 · Hartford, Conn · UCCL10604
- SLC to Mary M. Keller, 12 September 1890 · Tannersville, N.Y · UCCL04095
- OLC to Alice H. Day, 28 May 1891 · Hartford, Conn · UCCL04211
- OLC to Alice H. Day, 7 March 1892 · Menton, France · UCCL10526
- OLC to Ellen O’Neil, 30 May 1892 · Como, Italy · UCCL10613
- OLC to Alice H. Day, 23 February 1893 · Florence, Italy · UCCL10525
- OLC to Alice H. Day, 8 July 1893 · Munich, Germany · UCCL10524
- OLC to Alice H. Day, 27 August 1893 · Franzensbad, Germany · UCCL10522
- OLC to Alice H. Day, 5 September 1893 · Franzensbad, Germany · UCCL10523
- OLC to Alice H. Day, 9 September 1893 · Franzensbad, Germany · UCCL10521
- OLC to Alice H. Day, 10 October 1893 · Homburg, Germany · UCCL04472
- OLC to Alice Hooker Day, 4 February 1894 · Paris, France · UCCL10520
- OLC to Alice H. Day, 1 April 1894 · Paris, France · UCCL10519
- OLC to Alice H. Day, 23 May 1894 · Paris, France · UCCL10518
- OLC to Alice H. Day, 1 July 1894 · La Bourboule, France · UCCL10599
- Clara L. Clemens to Katherine S. Day, 29 July 1894 · Fluelen, Switzerland · UCCL04765
- OLC to Alice H. Day, 7 October 1894 · Rouen, France · UCCL10516
- SLC to Alice H. Day, 16 October 1894 · Rouen, France · UCCL04793
- OLC to Alice Hooker Day, 26 January 1895 · Paris, France · UCCL10598
- OLC to Alice H. Day, 3 February 1895 · Paris, France · UCCL10597
- OLC to Alice H. Day, 13 April 1896 · SS Wardha · UCCL05040
- OLC to Alice H. Day, 25 May 1896 · Durban, South Africa · UCCL10605
- Clara L. Clemens to Alice H. Day, 28 June 1896 · Cradock, South Africa · UCCL10621
- Clara L. Clemens to Katherine S. Day and Alice H. Day, 18 August 1896 · London, England · UCCL10623
- Clara L. Clemens to Alice H. Day, 11 September 1896 · London, England · UCCL05108
- Clara L. Clemens to Martha G. Pond, October–11 July 1897 · London, England · UCCL08585
- OLC to Alice H. Day, 22 October 1896 · London, England · UCCL10606
- OLC to Ellen O’Neil, 27 February 1898 · Vienna, Austria · UCCL10614
- OLC to Ellen O’Neil, 21 April 1898 · Vienna, Austria · UCCL10615
- OLC to John O’Neil, 27 October 1900 · New York, N.Y · UCCL10616
- SLC to George H. Keller, 25 November 1900 · New York, N.Y · UCCL05920
- Clara L. Clemens to Katherine S. Day, 21 December 1900 · New York, N.Y · UCCL10624
- SLC to Robert N. Stanley, 21 January 1901 · New York, N.Y · UCCL05973
- OLC to John O’Neil, 13 February 1901 · New York, N.Y · UCCL10617
- SLC to William Carey, 20 February 1901 · New York, N.Y · UCCL06006
- Clara L. Clemens to Katherine S. Day, 25 February 1901 · New York, N.Y · UCCL10625
- SLC to Mazie S. Robinson, 5 June 1901 · New York, N.Y · UCCL09793
- OLC to Alice H. Day, 18 August 1901 · New York, N.Y · UCCL10607
- OLC to Ellen O’Neil, 13 September 1901 · New York, N.Y · UCCL10618
- Clara L. Clemens to Katherine S. Day, November 1901 · Riverdale, N.Y · UCCL10626
- Clara L. Clemens to Katherine S. Day, 6 November 1901 · Riverdale, N.Y · UCCL10627
- OLC to John O’Neil, 29 November 1901 · Riverdale, N.Y · UCCL10619
- OLC to Ellen O’Neil, 23 December 1901 · Riverdale, N.Y · UCCL10620
- SLC to A. Schonstadt, 30 January 1902 · Riverdale, N.Y · UCCL10584
- Clara L. Clemens to Katherine S. Day, 11 September 1902 · York Harbor, Me · UCCL10628
- Clara L. Clemens to Katherine S. Day, 2 February 1903 · Riverdale, N.Y · UCCL10629
- Clara L. Clemens to Katherine S. Day, 18 June 1903 · Riverdale, N.Y · UCCL10630
- SLC to William H. Gillette, 22 October 1903 · New York, N.Y · UCCL06751
- Jean Clemens to Joseph H. Twichell, 14 June 1909 · Redding, Conn · UCCL10610
- Clara L. Clemens to Joseph H. Twichell, 26 September 1909 · Redding, Conn · UCCL10631
- Clara L. Clemens to Harmony C. Twichell, 1 October 1909 · Redding, Conn · UCCL10632
- Jean Clemens to Joseph H. Twichell, 17 October 1909 · Redding, Conn · UCCL10611
- Jean Clemens to Joseph H. Twichell, 27 November 1909 · Redding, Conn · UCCL10612
- Clara L. Clemens to Ida Langdon, 17 March 1910 · Monte Carlo, Monaco · UCCL10633
- Jean Clemens to John and Ellen O’Neil, 25 December n.y. · Unknown place · UCCL10634
- Susy (Olivia Susan) and Clara L. Clemens to Katherine S. Day and Alice H. Day, Unknown date, Hartford, Conn · UCCL10622
- SLC to Unidentified, Unknown date · Unknown place · UCCL10583
- SLC to Richard Eugene Burton, Unknown date · Hartford, Conn · UCCL07433
- SLC to ? Dunham, Unknown date · Unknown place · UCCL07643
- OLC to Katherine S. Day and Alice H. Day, Unknown date, Hartford, Conn · UCCL11119
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