A terrible and bloody Civil War freed enslaved Americans. The Fourteenth Amendment to the Constitution (1868) granted African Americans the rights of citizenship. However, this did not always translate into the ability to vote. Black voters were systematically turned away from state polling places. To combat this problem, Congress passed the Fifteenth Amendment in 1870. It says:
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.
Yet states still found ways to circumvent the Constitution and prevent blacks from voting. Poll taxes, literacy tests, fraud and intimidation all turned African Americans away from the polls. Until the Supreme Court struck it down in 1915, many states used the "grandfather clause " to keep descendents of slaves out of elections. The clause said you could not vote unless your grandfather had voted -- an impossibility for most people whose ancestors were slaves.
