Addressees: Hay, John M
- Samuel L. Clemens to John M. Hay, 6? January 1871 · Buffalo, N.Y · UCCL11849
- Samuel L. Clemens to John M. Hay, 12 January 1873 · Hartford, Conn · UCCL00856
- SLC to John M. Hay, 2 February 1899 · Vienna, Austria · UCCL05540
- SLC to John M. Hay, 11 March 1899 · Vienna, Austria · UCCL09028
- SLC to John M. Hay, 11 March 1899 · Vienna, Austria · UCCL05560
- SLC to John M. Hay, 4 May 1899 · Vienna, Austria · UCCL05586
- SLC to John M. Hay, 27 February 1900 · London, England · UCCL05764
- SLC to John M. Hay, 28 June 1901 · Saranac Lake, N.Y · UCCL06080
- SLC to John M. Hay, 11 March 1903 · Riverdale, N.Y · UCCL06596
- SLC to John M. Hay, 21 June 1904 · Florence, Italy · UCCL06850
- SLC to John M. Hay, 1905 · Unknown place · UCCL06976
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