After WW2 (as in 1947 or 1955 ???)
Well, it lost most of its original membership by 1930. The Knights of the Ku Klux Klan officially disbanded in 1944 after the IRS put a tax lien on them. Samuel Green then tried to recreate the group with the Association of Georgia Klans later that year. Both the FBI and the Georgia government investigated them, though, trying to shut them down, and they lost their official charter in 1947. Green died in 1949, and the AGK pretty much died with him.