Vigilantism - New Encyclopedia of the American West
The taking of the law into one’s own hands through the instrument of some type of extralegal committee has been part of the American experience since colonial days. It has taken various forms, ranging from unorganized mobs to quasi-military groups and operating under such names as Regulators, Moderators, Minutemen, and White Caps. Other groups, including the Ku Klux Klan, have incorporated vigilante functions into their activities. Although generally a rural phenomenon, some of the most notorious manifestations of vigilantism have occurred in cities.