The constitutional amendment that gave African American men the right to vote was the 15th Amendment. This was one of the so-called “Civil War Amendments” that were passed in an effort to end slavery and to make African Americans more or less legally equal to whites.
In the wake of the Civil War, the US ratified three new amendments to the Constitution. The first of these, the 13th Amendment, was ratified very quickly, becoming part of the Constitution in December of 1865. This amendment made slavery illegal in the US. Once this amendment was passed, leaders started to notice that African Americans were still being treated very poorly in Southern states. In order to limit this, they proposed the 14th Amendment. This amendment said that everyone in a state had to enjoy the “equal protection of the laws.” Seemingly, this meant that laws could not treat whites and blacks differently. The 14th Amendment was ratified in 1868.
Even after the 14th Amendment was passed, Republicans in the Congress worried that blacks would be deprived of the right to vote. Therefore, they passed the 15th Amendment. This amendment specified that people could not be deprived of the right to vote on the basis of “race, color, or previous condition of servitude.” This only allowed black men to vote as no women were allowed to vote in the US at this time. The 15th Amendment was ratified in 1870.
So, the amendment that gave African American men the legal right to vote was the 15th Amendment. This right was not really honored in most of the South, however, until the Voting Rights Act was passed almost 100 years later, in 1965.