In the 1950s, the house un-american activities committee blacklisted 320 people who were associated with

The correct answer is the entertainment industry.

The House Un-American Activities Committee - HUAC had the purpose of investigating people that were suspected of unpatriotic behavior - communism. The government believed that the communists were placing messages in Hollywood movies and because of that 320 people were associated with communism and their name was placed on a blacklist. This period is known as McCarthyism because of Senador Joseph McCarthy that led the investigations.

People who were blacklisted lost their jobs and spouses, could not find work anymore and had to move to Europe or other countries.