After the crusading idealism of World War I, America turned inward and became hostile to anything foreign or different. Radicals were targeted in the red scare and the Sacco-Vanzetti case, while the resurgent Ku Klux Klan joined other forces in bringing about pronounced restrictions on further immigration. Sharp cultural conflicts occurred over the prohibition experiment and evolution.

A new mass-consumption economy fueled the spectacular prosperity of the 1920s. The automobile industry, led by Henry Ford, transformed the economy and altered American lifestyles.

The pervasive media of radio and film altered popular culture and values. Birth control and Freudian psychology overturned traditional sexual standards, especially for women. Young literary rebels, many originally from the Midwest, scorned genteel New England and small-town culture and searched for new values as far away as Europe. The stock-market boom symbolized the free-wheeling spirit of the decade.