Weather Underground was a group of student activists who were deemed as a violent, radical, leftist group. During the 1970s, the group claimed responsibility for 12 bombings, including attacks on the U.S. Capital Building and the Pentagon.

Weather Underground, or Weathermen as they were later called, was formed after the Students for a Democratic Society (SDS) fragmented in the late 1960s. The members viewed themselves as a revolutionary organization whose purpose was to overthrow the United States government and the capitalist system. Their way of doing this was through riots and by carrying out a series of attacks, mostly bombings of government buildings.

Only a few members of the organization served any prison time in connection with bombings, riots and prison breaks carried out by group members. The information gathered against the group was said to have been obtained illegally by the now defunct Counter Intelligence Program.

Some of the Weathermen went on to different radical groups and have served long prison terms. Two of the members of the organization were pardoned by Bill Clinton.

Conservative advertisements have tried to link Democratic Presidential candidate Barack Obama to one of the Weather Underground's most prominent former members, current University of Illinois professor Bill Ayers. According to documents, Obama served alongside Ayers in community outreach programs, such as the educational initiative the "Chicago Annenberg Challenge."Fox News: Newly Released Documents Highlight Obama’s Relationship With Ayers (August 26, 2008)

• 1962: SDS holds its first convention
• 1965: First SDS anti-war march in Washington, DC
• 1970:
• March: 3 Weathermen are killed; Group becomes known as Weather Underground; Bernardine Dohrn, Bill Ayers and Kathy Boudin go into hiding
• June: Weather Underground takes credit for a NYPD headquarters bombing
• July: A New York bank is bombed in retaliation to 13 Weathermen being indicted on charges of conspiring to engage in acts of terrorism
• September: Member Timothy Leary escapes from prison with help of the Weathermen, issues a statement from the underground
• 1971: Weather Underground holds march on Washington DC with 50,000 anti-war protesters
• 1977: Mark Rudd and Cathy Wilkerson come out of hiding and surrender to police
• 1980: Bill Ayers and Bernardine Dohrn come out of hiding, both plead guilty to bail-jumping charges stemming from of a 1969 anti-war protest
• 1981: Unofficial end of the Weather Underground; Kathy Boudin comes out of hiding to participate in an armed robbery in New York
• 2003: Kathy Boudin is released from prison