Super Bowl IV: The Kansas City Chiefs beat the heavily favored Minnesota Vikings 23–7.
Black Sabbath's debut album, Black Sabbath released; often regarded as the first true heavy metal album
A bomb being constructed by members of the Weathermen and meant to be planted at a military dance in New Jersey, explodes, killing 3 members of the organization.
American President Richard Nixon signs the Public Health Cigarette Smoking Act into law, banning cigarette television advertisements in the United States with effect from January 1, 1971.
Kent State shootings: Four students at Kent State University in Ohio are killed and 9 wounded by Ohio State National Guardsmen, at a protest against the incursion into Cambodia.
June 10 – U.S. President Richard Nixon signs a measure lowering the voting age to 18.
The U.S. Food and Drug Administration (FDA) is subordinated to Public Health Service.
August 26 – The Women's Strike for Equality takes place down Fifth Avenue in New York City.
Vietnam War – Operation Jefferson Glenn: The United States 101st Airborne Division and the South Vietnamese 1st Infantry Division initiate a new operation in Thua Thien Province (the operation ends in October 1971).
National Educational Television ends operations, being succeeded by PBS.
Southern Airlines Flight 932 crashes in Wayne County, West Virginia; all 75 on board, including 37 players and 5 coaches from the Marshall University football team, are killed.
The United States Environmental Protection Agency begins operations.