Addressees: Howland, Robert M
- Samuel L. Clemens to Robert M. Howland, 29 October 1866 · Virginia City, Nev · UCCL00107 NvHi
- SLC to Robert M. Howland, 1 November 1866 · Virginia City, Nev · UCCL00062 CU-MARK
- Samuel L. Clemens to Robert M. and Louise M. Howland with a note to James W. Nye, 6 March 1870 · Buffalo, N.Y · UCCL00440 CU-MARK
- Samuel L. Clemens to Robert M. Howland, 1–6 or 12–21 June 1870 · Buffalo, N.Y · UCCL00476 CU-MARK
- Samuel L. Clemens to Robert M. and Louise M. Howland, 6 April 1871 · Elmira, N.Y · UCCL00600 CU-MARK
- Olivia L. and Samuel L. Clemens to Louise A. and Robert M. Howland, 3? September 1877 · Elmira, N.Y · UCCL04656 CU-MARK
- Samuel L. Clemens to Robert M. Howland, 27 October 1879 · Hartford, Conn · UCCL07428 CU-MARK, C10
- Samuel L. Clemens to Robert M. Howland, 14 December 1879 · Hartford, Conn · UCCL02810 CU-MARK
- Samuel L. Clemens to Robert M. Howland, 29 December 1879 · Hartford, Conn · UCCL04128 CU-MARK
- Samuel L. Clemens to Robert M. Howland, 2 May 1880 · Hartford, Conn · UCCL09310 CU-MARK
- SLC to Robert M. Howland, 15 January 1888 · Hartford, Conn · UCCL03700 CU-MARK
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