The Ku Klux Klan (KKK), or simply "the Klan", is the name of three distinct past and present movements in the United States, which have advocated extremist reactionary currents such as white supremacy, white nationalism, and anti-immigration, historically expressed through terrorism. The first organization sought to overthrow the Republican state governments in the South during the Reconstruction Era, especially by violence against African American leaders. It ended about 1871. The second was a very large nationwide organization in the 1920s that especially opposed Catholics. The current manifestation consists of numerous small unconnected groups that use the KKK name. All three movements have called for purification of American society, and all are considered part of right-wing extremism.
The current manifestation is classified as a hate group by the Anti-Defamation League and the Southern Poverty Law Center. It is estimated to have between 5,000 and 8,000 members as of 2012.
The first Ku Klux Klan flourished in the Southern United States in the late 1860s, then died out by the early 1870s. Members made their own, often colorful, costumes: robes, masks, and conical hats, designed to be outlandish and terrifying, and to hide their identities. The second KKK flourished nationwide in the early and mid-1920s, and adopted a standard white costume (sales of which together with initiation fees financed the movement) and code words as the first Klan, while adding cross burnings and mass parades. It stressed opposition to the Catholic Church. The third KKK emerged in the form of small local unconnected groups after 1950. They focused on opposition to the Civil Rights Movement, often using threats of violence. The second and third incarnations of the Ku Klux Klan made frequent reference to the America's "Anglo-Saxon" blood, harkening back to 19th-century nativism. Though most members of the KKK saw themselves as holding to American values and Christian morality, virtually every Christian denomination officially denounced the Ku Klux Klan.