National Portrait Gallery depicts the Sequoyah (d. 1843), the inventor of the Cherokee writing system. The script in Inman's painting doesn't look as well-executed as it could be; perhaps this is because Inman's work based upon a lost painting by Charles Bird King (King's painting was destroyed in a fire at the Smithsonian Castle).
signed his name as ᏍᏏᏉᏯ (Ssiquoya), but you can see here that he was also known by the English name of George Giss or Guess.
see this page.
To read (or hear) more about this painting, see this NPG blog posting. You can also read about the statue of Sequoyah in the National Statuary Hall Collection (see the next posting for more).