After the Thirteenth Amendment abolished slavery in 1865, those opposed to freedom for African Americans found other means of control. Southern states implemented restrictive laws known as Black Codes, and armed vigilantes formed the Ku Klux Klan and used violent intimidation. Several congressional committees investigated the Klan, and Congress passed the Enforcement Act of 1870 to protect freedmen against violence. A Joint Committee to Inquire into the Conditions of Affairs in the Late Insurrectionary States formed in 1871 and exposed the Klan’s tactics, hastening a decline that lasted until the 1920s.