An explosion at the Weather Underground safe house in Greenwich Village kills three.

The Weather Underground was a far-left Marxist militant organization first active in 1969, founded on the Ann Arbor campus of the University of Michigan. Originally known as the Weathermen, or simply Weatherman, the group was organized as a faction of Students for a Democratic Society (SDS) national leadership. 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 WUO believed to be imperialist.