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For the institution of slavery to have thrived in the United States, slave owners had had to use violence—or, more accurately, the threat of violence, reinforced constantly by its predictable, highly visual application against those enslaved. Precisely the same approach helped to secure the long reign of “emancipation without freedom” in the South.
White terrorist groups—chief among them the Ku Klux Klan—made sure African Americans lived in constant terror of random violence.
The white supremacist organization known as the Ku Klux Klan had two formal incarnations. The first, dating from 1866, was led by the former Confederate Nathan Bedford Forrest; it focused on wounding, murdering, and otherwise terrorizing African Americans, and on maintaining a racially divided society in which whites dominated. That version of the Klan was formally disbanded in 1869, although For-rest's followers continued to work in informal networks to deny African Americans their voting rights.
The Klan formally resurfaced in 1915, inspired to carry out a much broader mission of hatred. In response to large-scale immigration from Europe, the Klan added Catholics, Jews, and southern and eastern Europeans to its list of undesirables. This incarnation of the Klan, which took advantage of a wave of native-soil patriotism during the World War I period, proved extraordinarily popular not only in the South, but in certain Northern areas as well. (The movement was an extremely powerful political force, for instance, in the state of Kansas in the early and mid-1920s.)