Oh just had occasion to realize this wasn't common Amhist knowledge – there were three distinct foundings of the Ku Klux Klan with no actual continuity between them

The first one was in the immediate aftermath of the Civil War, measures were aimed at them by Reconstruction troops but it was really later, broader (less upper-class) groups like the White League and rifle clubs that overturned it and restored local white control

The second one in the 1910s was the one that really mattered, this important early movie "Birth of a Nation" retold a myth of the first one, added voguish Scottish historical romance elements (the movie invented those white hood costumes and cross-burning), and it was a huge cultural event.

Then someone built like, a mail-order fanclub (then a cutting edge thing!) around it, and then that got used as a critical element of a huge reactionary repressive wave that was so successful people don't believe that like, utopian pacifist socialist internationalist feminism had been a big thing before WWI. Anyway the second KKK effectively controlled many cities and even states.

The third one, inspired by the first two, the second having firmly set itself in mind as the idiom of the volk, was founded to resist the Civil Rights Movement but was cargo-culty and incompetent, not realizing what the second had done to succeed (articulate with other power centers, co-opt government) or even that the first failed. Modern groups are considered to come from the third founding.