The Cheyenne ( ) are one of the groups of  indigenous people of the Great Plains and their language is of the Algonquian language family. The Cheyenne comprise two Native American groups, the Só'taeo'o or Só'taétaneo'o (more commonly spelled as Suhtai or Sutaio) and the Tsétsêhéstâhese (also spelled Tsitsistas). These tribes merged in the early 19th century. Today the Cheyenne people are split into two federally recognized groups: Southern Cheyenne, who are enrolled in the Cheyenne and Arapaho Tribes in Oklahoma, and the Northern Cheyenne, who are enrolled in the Northern Cheyenne Tribe of the Northern Cheyenne Indian Reservation in Montana.