The Collaborative International Dictionary of English v.0.48:

Sagamore \Sag"a*more\, n.
   1. [Cf. Sachem.] The head of a tribe among the American
      Indians; a chief; -- generally used as synonymous with
      sachem, but some writters distinguished between them,
      making the sachem a chief of the first rank, and a
      sagamore one of the second rank. "Be it sagamore, sachem,
      or powwow." --Longfellow.
      [1913 Webster]

   2. A juice used in medicine. [Obs.] --Johnson.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sagamore
    n 1: a chief of a North American tribe or confederation
         (especially an Algonquian chief) [syn: sachem,
         sagamore]