The Fifteenth Amendment to the United States Constitution, ratified in 1870, prohibits the federal and state governments from denying a citizen the right to vote based on 'race, color, or previous condition of servitude.' This amendment was a critical step in the ongoing struggle for civil rights and aimed to ensure that African American men could participate in the political process. It is a key aspect of voting rights history, laying the groundwork for further legislation aimed at combating racial discrimination in voting.