Earlier in the twentieth century, Dr Grace Raymond Hebard of the University of Wyoming, a political economist, not a historian or anthropologist, argued that Charbonneau died and was buried at the Shoshone Wind River Indian Reservation. Dr. Charles Eastman, a Santee Sioux and not of the Shoshone language group, did research that attempted to establish that Charbonneau's mother Sacagawea died at the reservation on April 9, 1884. Some believe that Charbonneau died in 1885 and was buried next to her. Memorials in their names were erected in 1933 at Ft. Washakie. Eastman did his research in 1924–25, interpreting oral history. But his translation has been superseded by documentary evidence for both Charbonneau and Sacagawea.