Three separate Klans have existed in three non-overlapping time periods. Each comprised local chapters with little or no central direction. Each has advocated extremist reactionary positions such as white nationalism, anti-immigration and—especially in later iterations—Nordicism, antisemitism, anti-Catholicism, Prohibition, right-wing populism, anti-communism, homophobia, anti-atheism, and Islamophobia. The first Klan founded by Confederate veterans used terrorism—both physical assault and murder—against politically active Black people and their allies in the Southern United States in the late 1860s. The second iteration of the Klan originated in the late 1910s, and was the first to use cross burnings and hooded robes. The KKK of the 1920s had a nationwide membership in the millions and reflected a cross-section of the native-born white population. The third Klan formed in the mid 20th century, largely as a reaction to the growing civil rights movement. It committed murders and bombings to achieve its aims. All three movements have called for the "purification" of American society, and are all considered far-right extremist organizations. In each era, membership was secret and estimates of the total were highly exaggerated by both friends and enemies.