His most important works are "Social Darwinism in American Thought, 1860–1915" (1944); "The American Political Tradition" (1948); "The Age of Reform" (1955); "Anti-intellectualism in American Life" (1963), and the essays collected in "The Paranoid Style in American Politics" (1964). He was awarded the Pulitzer Prize two times: in 1956 and 1964.