The Ku Klux Klan (KKK) had a resurgence in the 1920s. Its resurgence came about because of changes to society that made American society more modern. The KKK was based largely on a desire to have society return to traditional ways.
In the 1920s, the United States was moving away from traditional ways in a number of respects. For one thing, it had become a country with a large number of immigrants. Many of these immigrants were not Protestant but were, instead, Jewish or Catholic. A second factor was the changing of values in the cities. This was the time of the “flappers” and jazz. It was a time when women were doing things like smoking in public and sexual values were supposedly deteriorating. All of these things bothered people who believed in traditional morals.
This led to the resurgence of the KKK. It promised “100% Americanism.” It opposed immigrants and it opposed Jews and Catholics. It wanted a return to the old social and moral values. In other words, it got its impetus from the backlash that was arising among many people against the new ways.