The Danites were a fraternal organization founded by Latter Day Saint (LDS) members in June 1838, in the town of Far West in Caldwell County, Missouri. During their period of organization in Missouri, the Danites operated as a vigilante group and took a central role in the events of the 1838 Mormon War. Whether or not the Danites existed after the 1847 arrival of the LDS in Utah is still debated. However, they remained an important part of Mormon and non-Mormon folklore, polemics, and propaganda for the remainder of the 19th century, waning in ideological prominence after Utah gained statehood. Notwithstanding public excommunications of Danite leaders by the Church and both public and private statements from Joseph Smith referring to the band as being both evil in nature and a "secret combination" (i.e., a derogatory term used in the Book of Mormon) to which he attributed no part of, the nature and scope of the organization, and the degree to which it was officially connected to The Church of Jesus Christ of Latter-day Saints, are a matter of some dispute among historians. Earlier in the band's existence, Joseph Smith appeared to endorse the group's actions, but later turned against them as violence increased and the actions of the Danites inspired a hysteria in Missouri that eventually led to the Extermination Order.
Source: Wikipedia http://en.wikipedia.org/wiki/Danites