Final answer:
The Red Scare, characterized by fear of communism and radical ideologies, was prompted by the rise of the Socialist Party and an influx of immigrants, leading to widespread suspicion and discrimination in the 1920s.
Step-by-step explanation:
The rise of the Socialist Party and the influx of southern and eastern European immigrants to the United States prompted the event that became known as the Red Scare. During the 1920s, fears of a leftist revolution, similar to the Bolshevik Revolution in Russia, led to widespread suspicion and discrimination against those who espoused socialism, anarchism, or other radical political ideas. The Red Scare was characterized by fear that communist infiltrators sought to overthrow the American government. High-profile events, such as bombings and the trial of Sacco and Vanzetti, fueled this climate of fear and distrust, particularly against foreigners who were often associated with these radical ideologies.