Ku Klux Klan Act (1871)
In the years after the Civil War, the South began to see the emergence of white terrorist groups. These organizations of composed mostly of veterans still aspring to the goals of the Confederacy and their own Southern heritage, brought terror to freed blacks who looked to participate in the community as well as to their white allies. The Ku Klux Klan Act of 1871 was Congress' attempt to put an end to the policies of terrorism, intimidation, and violence that the Klan, the Knights of the White Camelia, and the Jayhawkers had been using. The law unfortunately failed to eradicate the Klan or abolish the continued use of fear tactics and brutality against blacks and supportive whites.
Source: The African American Almanac, Eighth Editition "Significant Documents in African American History"