The Ku Klux Klan (KKK) was founded in the South during the Reconstruction period, but its membership tapered off in the 1870s. The Klan was revived in 1915 in Georgia and gained significant influence throughout the United States during the 1920s, partly due to the release of the film The Birth of a Nation.

The KKK is a white supremacist domestic terrorism organization that targets African Americans, Jews, Catholics, immigrants, and homosexuals. It has used physical assault and murder, particularly against African Americans, in an effort to suppress their political freedoms. Since its founding, the Klan has promoted a "purification" agenda, opposing racial equality and maintaining a long-held belief in white superiority.

The Klan is notorious for its uniform, which includes white robes, conical hats, and masks to conceal the identities of its members.