The Twenty-sixth Amendment is ratified
The Twenty-sixth Amendment (Amendment XXVI) to the United States Constitution standardized the voting age to 18.
It was adopted in response to student activism against the Vietnam War and to partially overrule the Supreme Court's decision in Oregon v. Mitchell. It was adopted on July 1, 1971. The voting age had previously been 21.
Section 1. The right of citizens of the United States, who are eighteen years of age or older, to vote shall not be denied or abridged by the United States or by any State on account of age.
Section 2. The Congress shall have the power to enforce this article by appropriate legislation.
”— 26th Amendment to the United States Constitution
United States Amendments