The roots of the House Un-American Activities Committee go back to the 1930's when it was initially known as the Special Committee on Un-American Activity.
Created by the Liberal Democratic Senator from New York Samuel Dickenstein, the main focus of its investigations were domestic American Fascism and Nazism. In 1938, with its status as a committee of the House of Representatives extended and now under the leadership of conservative House member Martin Dies, its new task was to investigate subversive organizations and unamerican propaganda; this quickly took an anti-communist tone under the aggressive leadership of its conservative chairman. The Dies committee, as it was known, also became a convenient conservative tool for reducing many hated New Deal programs by linking them with the taint of Communism.
The Federal Theater Project, a New Deal initiative that kept actors employed, was investigated by Dies for its alleged Communist themes. In 1941, a colleague of Dies', Jack Tenney, started his own commission in California investigating subversive activity, a decision partly inspired by Disney himself. The first person that Tenney called to testify was Herbert Sorell, the man that was responsible for unionizing Disney studio employees.
By the time 1947 came around, HUAC was a permanent standing committee and refocused its efforts once more towards subversiveness in Hollywood. As the authors of The Inquisition in Hollywood have put it:
“Like a beacon in the darkening political night of postwar America, Hollywood attracted the moths of reaction again and again.”
But in 1947, there was also an unprecedented amount of new measures taken to clamp down on Communist influence, with HUAC being but one of them. The Taft-Hartley Act, which sought to reduce the power of Unions and Communist influence within them and the Federal governments loyalty-security programs for federal employees, were both instituted in the same year setting the stage for HUAC.
This is not to say of course that political anti-communism had not existed prior to HUAC. As Ellen Schreker has noted, anticommunist forces would first come to influence national politics during World War I, when “national security became central to the repression of left-wing dissent.” She goes on to document the many political uses of the wartime espionage and sedition laws to stifle union activity and fight the “reds.”28 But it is important to recognize as well that the climate of McCarthyism was reflective of the high level of anxiety in American post-war society and the highly corrosive influence of a minority of powerful Conservative figures who had the ability to push their anti-liberal agenda. These Conservatives included the likes of Eric Johnston, the President of the Motion Pictures Producers' Association, who cooperated with the Hollywood investigations and engaged in self-censorship.
Another more notable Conservative who was only too willing to cooperate with the Hollywood investigations was Walt Disney himself.