The Collaborative International Dictionary of English v.0.48:

Quadroon \Quad*roon"\, n. [F. quarteron, or Sp. cuarteron. See
   Quarter a fourth part, and cf. Quarteron.]
   The offspring of a mulatto and a white person; a person
   quarter-blooded. [Written also quarteron, quarteroon, and
   quateron.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Quarteron \Quar"ter*on\, Quarteroon \Quar"ter*oon\, n.
   A quadroon.
   [1913 Webster]