Addressees: Underhill, Charles M
- Samuel L. Clemens to Charles M. Underhill, 6 August 1872 · New Saybrook, Conn · UCCL08840
- SLC to Charles M. Underhill, 17 July 1886 · Elmira, N.Y · UCCL02638
- SLC to Charles M. Underhill, 10 December 1889 · Hartford, Conn · UCCL10799
- SLC to Charles M. Underhill, 14 April 1893 · Chicago, Ill · UCCL04374
- SLC to Charles M. Underhill, ca 20–22 April 1893 · Chicago, Ill · UCCL13300
- SLC to Charles M. Underhill, 27 October 1902 · Riverdale, N.Y · UCCL08232
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