The Hollywoo blacklist—more precisely the entertainment industry blacklist, into which it expanded—was the mid-twentieth-century list of screenwriters, actors, directors, musicians, and other U.S. entertainment professionals who were denied employment in the field because of their political beliefs or associations, real or suspected. Artists were barred from work on the basis of their alleged membership in or sympathy toward the American Communist Party, involvement in liberal or humanitarian political causes that enforcers of the blacklist associated with communism, and/or refusal to assist federal investigations into Communist Party activities; some were blacklisted merely because their names came up at the wrong place and time. Even during the period of its strictest enforcement, the late 1940s through the late 1950s, the blacklist was rarely made explicit and verifiable, but it caused direct damage to the careers of scores of American artists, often made betrayal of friendship (not to mention principle) the price for a livelihood, and promoted ideological censorship across the entire industry.