The Fifteenth Amendment (Amendment XV) of the United States Constitution prohibits each government in the United States to prevent a citizen from voting based on that citizen's race, color, or previous condition of servitude (i.e., slavery). It was ratified on February 3, 1870.
Section 1. 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.
Section 2. The Congress shall have power to enforce this article by appropriate legislation.
Of this there can be no doubt. At the time of the ratification of the Articles of Confederation, all free native-born inhabitants of the States of New Hampshire, Massachusetts, New York, New Jersey, and North Carolina, though descended from African slaves, were not only citizens of those States, but such of them as had the other necessary qualifications possessed the franchise of electors, on equal terms with other citizens.
The first person to vote under the provisions of the amendment was Thomas Mundy Peterson who cast his ballot in a Perth Amboy school board election being held on March 31, 1870. It was not until the Voting Rights Act of 1965, almost a century later, that the full promise of the Fifteenth Amendment was actually achieved in all states. After the passage on a per capita and absolute basis, more blacks were elected to political office during the period from 1865 to 1880 than at any other time in American history. Although no state elected a black governor during Reconstruction, a number of state legislatures were effectively under the control of a substantial African American caucus. These legislatures brought in programs that are considered part of government's duty now, but at the time were radical, such as universal public education. They also set aside all racially biased laws, including anti-miscegenation laws (laws prohibiting interracial marriage).
Despite the efforts of groups like the Ku Klux Klan to intimidate black voters and white Republicans, assurance of federal support for democratically elected southern governments meant that most Republican voters could both vote and rule in confidence. For example, when an all-white mob attempted to take over the interracial government of New Orleans, President Ulysses S. Grant sent in federal troops to restore the elected mayor.
However, after the close election of Rutherford B. Hayes, Hayes, in order to mollify the South, agreed to withdraw federal troops. He also overlooked poll violence in the deep south, despite several attempts by the Republicans to pass laws assuring the rights of black voters and to punish intimidation. To show the unwillingness of Congress to take any action at this time, even a bill that would have required incidents of violence only at polling places to be publicized failed to be passed. Without the restrictions, voting place violence against blacks and Republicans increased, including instances of murder. Most of this was done without any interference by law enforcement, and often even with their co-operation.
The original House and Senate draft of the Amendment stated that the right to vote and to be a candidate would not be denied or abridged by the States based on race, color or creed. This was eventually omitted due to the desire among many Northern Republicans to leave their own laws limiting black participation in government intact. The amendment did not establish true universal male suffrage partly because Southern Republicans were afraid to undermine loyalty tests, which the Reconstruction state governments used to limit the influence of ex-Confederates.