The Voting Rights Act was signed into law on August 6, 1965, by President Lyndon Johnson. It outlawed the discriminatory voting practices adopted in many southern states after the Civil War, including literacy tests as a prerequisite to voting.
This “act to enforce the fifteenth amendment to the Constitution” was signed into law 95 years after the amendment was ratified. In those years, African Americans in the South faced tremendous obstacles to voting, including poll taxes, literacy tests, and other bureaucratic restrictions to deny them the right to vote. They also risked harassment, intimidation, economic reprisals, and physical violence when they tried to register or vote. As a result, African-American voter registration was limited, along with political power.
Source: https://www.archives.gov/milestone-documents/voting-rights-act