The document provides a summary of the Ku Klux Klan as the oldest and most infamous American hate group. It describes the KKK's origins in the post-Civil War South to terrorize blacks and promote white supremacy. The document outlines three distinct movements of the KKK from 1865 to the present day, tracing its evolution from targeting black political leaders to later immigrants and minorities as well. Key beliefs of the KKK discussed include white nationalism, anti-immigration, anti-Semitism, and purifying American society along white supremacist ideals.