At the turn of the 20th , America's social was changing rapidly. Urbanization, industrialization and a massive influx in Jewish and Catholic from Europe. The Klan began a violent to terrorize immigrants, and exploit fears that immigrants threatened American values.

In the 1920s, klan membership was over four million. During the 1930s and 40s, klan membership again declined but the klan experienced a resurgence during the era.

In the 1950s, blacks began to demand an end to the in the , that legally supported . Seeing the as a threat to white rule, the klan went on the attack.

Between 1955 and 1965, klansmen or clan sympathizers carried out over 200 bombings and 40 civil rights workers. Brutal images of klan turned against the KKK. By the end of the 1960s, the FBI was successfully infiltrating the klan and its leaders were being prosecuted. It seemed the clan had been defeated. Klan membership declined from nearly 40,000 in to a low of 1500 in .

But over their long history, the Ku Klux Klan has always managed to rebuild.