Source : Webster's Revised Unabridged Dictionary (1913)

Dakotas \Da*ko"tas\, n. pl.; sing. {Dacota}. (Ethnol.)
   An extensive race or stock of Indians, including many tribes,
   mostly dwelling west of the Mississippi River; -- also, in
   part, called {Sioux}. [Written also {Dacotahs}.]

Dacotahs \Da*co"tahs\, n. pl.; sing. {Dacotan}. (Ethnol.)
   Same as {Dacotas}. --Longfellow.