Contrary to popular myth, the United States was not founded on the concept of "one person, one vote." In fact, there isn't a right to vote enshrined in the Constitution at all, a fact which the late Justice Antonin Scalia made sure to mention in his notorious Bush v. Gore opinion that decided the 2000 election. Managing elections was at first left entirely up to the states, which meant that in most places, most of the time, only white male landowners had the franchise. It took several decades, until the Andrew Jackson era, before essentially all white men were allowed to vote, let alone anyone else. (A few property-owning African Americans were permitted to vote in Northern cities before the Civil War, but no women could vote anywhere until Wyoming enacted universal suffrage in 1869.)
After the Civil War, the end of slavery and the 14th Amendment, all Black men were officially granted citizenship, but very few were allowed to vote before the enactment of the 15th Amendment in 1870, which specified that the right 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." That led to the brief period of Reconstruction, which saw Black men not just voting across the South but also elected to high office: Sixteen African Americans served in Congress (including two U.S. senators) and several hundred served in state legislatures. But by the 1880s all that was over, as Southern whites (with the federal government's permission) launched the systematic disenfranchisement, vote suppression and voter intimidation of the Jim Crow era, meaning that virtually no Black people in the South could vote until the civil rights movement of the 1950s and '60s led to the passage of the Voting Rights Act.
