What was different about the KKK in the 1920s as compared to the KKK right after the
Civil War?

The Ku Klux Klan, founded in the late 1860’s, experiences three major surges in popularity promoting ideals such as white supremacy, white nationalism, Nativism, anti-immigration, and anti-communism.

Explanation: The first era of Ku Klux Klan experienced a rise in popularity in the late 1800’s with the intent of overthrowing Republican state governments in the South and ensuring that newly-freed southern African Americans did not vote. In 1871 their membership was oppressed by federal law enforcement (1871 Ku Klux Klan Act signed by President Grant to combat the KKK and other white supremacy groups).  

The second Ku Klux Klan group flourished nationwide in the 1920’s on the platform of pro-prohibition and anti-Catholicism and anti-Jewish feelings. They experience a diminished population in the late 1920’s (around the time of the Great Depression; a time of mass American economic hardship).  

The modern-day third wave of the Ku Klux Klan came about in the late 1950’s opposing the civil rights movement. Current membership, as of 2016, amounts to an estimated 3,000-6,000 active members.