The Fifteenth Amendment to the United States Constitution is ratified, guaranteeing voting rights to male citizens regardless of race.

The Fifteenth Amendment (Amendment XV) to the United States Constitution prohibits the federal government and each state from denying or abridging a citizen's right to vote "on account of race, color, or previous condition of servitude." It was ratified on February 3, 1870, as the third and last of the Reconstruction Amendments.

In the final years of the American Civil War and the Reconstruction Era that followed, Congress repeatedly debated the rights of the millions of former black slaves. By 1869, amendments had been passed to abolish slavery and provide citizenship and equal protection under the laws, but the election of Ulysses S. Grant to the presidency in 1868 convinced a majority of Republicans that protecting the franchise of black male voters was important for the party's future. On February 26, 1869, after rejecting more sweeping versions of a suffrage amendment, Congress proposed a compromise amendment banning franchise restrictions on the basis of race, color, or previous servitude. After surviving a difficult ratification fight, the amendment was certified as duly ratified and part of the Constitution on March 30, 1870.

United States Supreme Court decisions in the late nineteenth century interpreted the amendment narrowly. From 1890 to 1910, southern states adopted new state constitutions and enacted laws that raised barriers to voter registration. This resulted in most black voters and many poor white ones being disenfranchised by poll taxes and discriminatory literacy tests, among other barriers to voting, from which white male voters were exempted by grandfather clauses. A system of white primaries and violent intimidation by white groups also suppressed black participation.

In the twentieth century, the Court began to interpret the amendment more broadly, striking down grandfather clauses in Guinn v. United States (1915) and dismantling the white primary system in the "Texas primary cases" (1927–1953). Voting rights were further incorporated into the Constitution in the Nineteenth Amendment (voting rights for women) and the Twenty-fourth Amendment (prohibiting poll taxes in federal elections). The Voting Rights Act of 1965 provided federal oversight of elections in discriminatory jurisdictions, banned literacy tests and similar discriminatory devices, and created legal remedies for people affected by voting discrimination. The Court also found poll taxes in state election unconstitutional under the Fourteenth Amendment in Harper v. Virginia State Board of Elections (1966).