vigilante

In US history, originally a member of a ‘vigilance committee’, a self-appointed group to maintain public order in the absence of organized authority, especially in Western frontier communities.

Early vigilante groups included the ‘Regulators’ in South Carolina in the 1760s and in Pennsylvania 1794 during the Whiskey Rebellion. Many more appeared in the 19th century in frontier towns. Once authorized police forces existed, certain vigilante groups, such as the post-Civil War racist Ku Klux Klan, operated outside the law, often as perpetrators of mob violence such as lynching.