Rise of the KKK is an American event that can happen after the Civil War. It signifies the creation of the Infamous Ku Klux KlanIt can happen if 
Confederate States of America doesn't exist and 
USA has taken the decision Radical Reconstruction and owns Richmond, Mongomery and New Orleans.
It has a mean time to happen of 30 months (roughly 2.5 years) and gives all Dixie POPs 3 militancy and 1 consciousness.
The amount of militancy and consciousness given by this event is lower than the amount removed by Radical Reconstruction, so one should not refrain from taking the decision.