Macro-Siouan languages
In the 19th century, Robert Latham suggested that the Siouan languages are related to the Caddoan and Iroquoian languages. In 1931, Louis Allen presented the first list of systematic correspondences between a set of 25 lexical items in Siouan and Iroquoian. In the 1960s and 1970s, Wallace Chafe further explored the link between Siouan and Caddoan languages. In the 1990s, Marianne Mithun compared the morphology and syntax of all the three families. At present, the Macro-Siouan hypothesis based on relations among Siouan, Caddoan, and Iroquoian is not universally accepted as proven.
Fort Ancient
Here, Fort Ancient culture was at its height. Only one known Fort Ancient tribe has been verified by name in the historical record-- the Mosopelea, presumably of southeast Ohio. There is also a chance that a Siouan people called the Keyauwee, who appear alongside the Tutelo (an Eastern Siouan tribe from West Virginia) in North Carolina around 1700 could also have been of Fort Ancient stock. During the French explorations, a Ho-chunk native named Tonti told them that these people had been known as the "Chonque". Mosopelea language is marked as being the only known Siouan tongue to use the "f" sound, which is far more common among the Muskogean languages of the Mississippians.