The Fifteenth Amendment to the United States Constitution was passed on February 3, 1870 which protected the right of African-Americans to vote.
It reads,
Section 1. The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of race, color, or previous condition of servitude.
Section 2. The Congress shall have power to enforce this article by appropriate legislation.
Of course this wasn’t the end of discriminatory disenfranchisement practices which went on for another century in this country with acts of violence and intimidation, the Jim Crowe laws, literacy tests, etc. These efforts at going around the Fifteenth Amendment were addressed by the Voting Rights Act passed in 1965 during the height of the Civil Rights Movement.
