Source : Webster's Revised Unabridged Dictionary (1913)

Mackinaw blanket \Mack"i*naw blan"ket\, Mackinaw \Mack"i*naw\
   [From Mackinac, the State of Michigan, where blankets and
   other stores were distributed to the Indians.]
   A thick blanket formerly in common use in the western part of
   the United States.

Source : WordNet®

Mackinaw blanket
     n : a thick plaid blanket formerly used in the northwestern
         United States [syn: {mackinaw}]