His revisionist study of the conservative interests of the drafters of the U.S. Constitutional Convention, (An Economic Interpretation of the Constitution) seemed radical in 1913.
After resigning from Columbia University in World War I, he helped to found the New School for Social Research in New York, and advised on reconstructing Tokyo after the earthquake of 1923.
Beard's reputation still rests on his wide-ranging The Rise of American Civilization (1927) and its two sequels, America in Midpassage (1939), and The American Spirit (1943), all written in collaboration with his wife, Mary Ritter Beard (1876–1958) whose own interests lay in feminism and the labor movement (Woman as a Force in History, 1946). Together they wrote a popular survey, The Beards’ Basic History of the United States.
Charles Beard was critical of Franklin D. Roosevelt’s administration, especially in the struggle over the Supreme Court and in FDR's foreign policy. Beard’s last work was President Roosevelt and the Coming of the War (1948)