Arikara is a Caddoan language spoken by the Arikara Native Americans who reside primarily at Fort Berthold Reservation in North Dakota. Arikara is very close to the Pawnee language, but they are not mutually intelligible.The Arikara were apparently a group met by Lewis and Clark in 1804; their population of 30,000 was reduced to 6,000 by Smallpox.