The Weather Underground was an American Marxist militant organization active from 1969 until 1977. Originally known as the Weathermen, or simply Weatherman, the group was organized as a faction of the national leadership of Students for a Democratic Society (SDS). Officially known as the Weather Underground Organization (WUO) beginning in 1970, the group's express political goal was to create a revolutionary party to overthrow the United States government, which the WUO viewed as imperialist.