The Ku Klux Klan (KKK), or simply "the Klan", is the name of three distinct past and present movements in the United States that have advocated extremist reactionary currents such as white supremacy, white nationalism, anti-immigration, and, especially in later iterations, Nordicism,[6][7] anti-Catholicism,[8][9] and anti-Semitism,[9] historically expressed through terrorism aimed at groups or individuals whom they opposed.[10] All three movements have called for the "purification" of American society, and all are considered right wing extremist organizations.[11][12][13][14]

The first Klan flourished in the Southern United States in the late 1860s, then died out by the early 1870s. It sought to overthrow the Republican state governments in the South during the Reconstruction Era, especially by using violence against African American leaders. With numerous chapters across the South, it was suppressed around 1871, through federal enforcement. Members made their own, often colorful, costumes: robes, masks, and conical hats, designed to be terrifying, and to hide their identities.[15][16]

The second group was founded in 1915, and flourished nationwide in the early and mid-1920s, particularly in urban areas of the Midwest and West. It opposed Catholics and Jews, especially newer immigrants, and stressed opposition to the Catholic Church.[17] This second organization adopted a standard white costume and used similar code words as the first Klan, while adding cross burnings and mass parades.

The third and current manifestation of the KKK emerged after 1950, in the form of small, local, unconnected groups that use the KKK name. They focused on opposition to the Civil Rights Movement, often using violence and murder to suppress activists. It is classified as a hate group by the Anti-Defamation League and the Southern Poverty Law Center.[18] It is estimated to have between 5,000 and 8,000 members as of 2012.[2]

The second and third incarnations of the Ku Klux Klan made frequent references to America's "Anglo-Saxon" blood, hearkening back to 19th-century nativism.[19] Although members of the KKK swear to uphold Christian morality, virtually every Christian denomination has officially denounced the KKK.[20]