Family of North American Indian languages, spoken mainly west of the Mississippi River in the 17th and 18th centuries.
The principal languages and language groups at this time were Winnebago in Wisconsin, Chiwere (Iowa, Oto, and Missouri) in Iowa and northern Missouri, Dhegiha (Ponca, Omaha, Kansa, Osage, Quapaw) in an area extending from eastern Nebraska to Arkansas, Sioux or Dakota (a range of dialects including Santee or Dakota proper in Minnesota, Teton or Lakota in North and South Dakota, and Assiniboine in Canada), Hidatsa and Mandan on the middle Missouri River, and Crow in Wyoming and Montana. Separated from the main body of Siouan languages were the now-extinct languages Tufelo and Biloxi, near the Gulf of Mexico, and the distantly related Catawba, once spoken in South Carolina. The extant Siouan languages are now spoken mainly or solely by older adults.