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 black freedmen. 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, Republicans proposed a compromise amendment which would ban franchise restrictions on the basis of race, color, or previous servitude. After surviving a difficult ratification fight and opposition from Democrats, the amendment was certified as duly ratified and part of the Constitution on March 30, 1870. According to the Library of Congress, in the House of Representatives 144 Republicans voted to approve the 15th Amendment, with zero Democrats in favor, 39 no votes, and seven abstentions. In the Senate, 33 Republicans voted to approve, again with zero Democrats in favor.
United States Supreme Court decisions in the late nineteenth century interpreted the amendment narrowly. From 1890 to 1910, the Democratic Party in the Southern United States adopted new state constitutions and enacted "Jim Crow" laws that raised barriers to voter registration. This resulted in most black voters and many Poor Whites 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 Democrats through the Ku Klux Klan (KKK) also suppressed black participation.