Final answer:
The Ku Klux Klan used violence and intimidation to oppose African American rights and restore white supremacy post-Civil War and worked as an extension of the Democratic Party.
Step-by-step explanation:
The organization known for using violence to intimidate people, especially during the Reconstruction era in the United States, was the Ku Klux Klan (KKK). Originally formed by Confederate veterans, the Klan aimed to restore white supremacy by terrorizing African Americans and their allies. Their acts of violence included intimidation, lynchings, and political assassinations, targeting not only African Americans but also northerners, known as carpetbaggers, and southern whites who supported Reconstruction, referred to as scalawags. To control the political power in the South, they also functioned as an arm of the Democratic Party during elections. Despite federal efforts to curb terrorism through the Enforcement Acts, the KKK and similar organizations persisted in their efforts to maintain racial hierarchies.