The 20th c. KKK across the United States was a fraternal organization, but dunno who started it. I remember it had about 5 million members. Don't know any details. I remember people being surprised when going through family papers and finding a father's or grandfather's membership card- but if he was an independent business man or farmer, chances were good that he had been a member. The group seems to have died a death from general uselessness.

I have also heard that the KKK in the South during the 20th c. mostly was more informal, the headquarters in a small town being a local barber shop or pool hall. Several groups with leaders, mostly self-proclaimed.