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The United States Constitution's 26th Amendment, which lowers the voting age from 21 to 18, is signed by President Richard Nixon.
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Women are granted the right to vote in the US by a vote of 278–124 in the House of Representatives.
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In the United States, the inaugural Earth Day is observed, commemorating the start of the contemporary environmental movement.
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During a protest against the Vietnam War at Kent State University, Ohio National Guardsmen shoot and murder four students, injuring nine more. This incident is known as the Kent State shootings.
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The United States Constitution's 26th Amendment, which lowers the voting age from 21 to 18, is signed by President Richard Nixon.
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The United States Senate confirms Harry Blackmun as a Justice of the Supreme Court of the United States.
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At the Army Mathematics Research Center at the University of Wisconsin–Madison, a bomb planted by anti-war radicals detonates, killing one researcher and wounding three more.