How did the twenty-fourth amendment affect the voting rights of african americans

It prevented states from collecting a poll tax that discouraged poor African Americans from voting.

"Poll taxes were enacted in many southern states to keep Blacks from voting.  At the time the amendment was ratified, Alabama, Arkansas, Mississippi, Texas, and Virginia still had poll taxes.  In fact, Mississippi was the only state to reject the amendment.

The 24th Amendment also gave Congress power to enforce it.  A year and a half later on August 6, 1965, the Voting Rights Act was enacted and banned poll taxes in all U.S. elections."

Explanation:

"The amendment forbids Congress and states from requiring poll taxes in order to vote in federal elections.  

Amendments to the Constitution are proposed by both houses in Congress and require two-thirds of the states to ratify, or approve, them. South Dakota ratified the amendment on January 23, 1964, which made the amendment go into effect."

Reference:  The Leadership Conference on Civil and Human Rights/The Leadership Conference Education Fund. “Today in Civil Rights History: The 24th Amendment Prohibits Poll Taxes.” The Leadership Conference on Civil and Human Rights, 1 Feb. 2019,