African-Americans were granted the right to vote in elections in the United States when the 15th Amendment to the U.S. Constitution was ratified on Feb. 3, 1870. It was the last of the three Reconstruction Amendments, which were ratified just after the American Civil War ended in 1865.
After the Amendment passed, the South resisted the new law and created obstacles to prevent former slaves from voting, such as literacy tests, poll taxes and grandfather clauses. These were found to be unconstitutional by the Supreme Court.
The amendment gave African-American men the right to vote but not African-American women. Women did not get the right to vote until the 19th Amendment was passed in 1920.