The adoption of the Thirteenth, Fourteenth, and Fifteenth Amendments to the Constitution extended civil and legal protections to former slaves and prohibited states from disenfranchising voters “on account of race, color, or previous condition of servitude.” Forces in some states were at work, however, to deny black citizens their legal rights. Members of the Ku Klux Klan, for example, terrorized black citizens for exercising their right to vote, running for public office, and serving on juries. In response, Congress passed a series of Enforcement Acts in 1870 and 1871 (also known as the Force Acts) to end such violence and empower the president to use military force to protect African Americans.
In its first effort to counteract such use of violence and intimidation, Congress passed the Enforcement Act of May 1870, which prohibited groups of people from banding together "or to go in disguise upon the public highways, or upon the premises of another" with the intention of violating citizens’ constitutional rights. Even this legislation did not diminish harassment of black voters in some areas.
In December 1870, Senator Oliver H.P.T. Morton, an Indiana Republican, introduced a resolution requesting the president to communicate any information he had about certain incidents of threatened resistance to the execution of the laws of the United States. After the Senate adopted Morton's resolution, President Ulysses S. Grant submitted several War Department reports relating to events in several southern states. These reports were referred to the Select Committee of the Senate to Investigate the Alleged Outrages in the Southern States, chaired by Senator Henry Wilson of Massachusetts. In the next Congress the Joint Select Committee to Inquire into the Condition of Affairs in the Late Insurrectionary States broadened that mandate.
While these committees were investigating southern attempts to impede Reconstruction, the Senate passed two more Force acts, also known as the Ku Klux Klan acts, designed to enforce the Fourteenth Amendment and the Civil Rights Act of 1866. The Second Force Act, which became law in February 1871, placed administration of national elections under the control of the federal government and empowered federal judges and United States marshals to supervise local polling places. The Third Force Act, dated April 1871, empowered the president to use the armed forces to combat those who conspired to deny equal protection of the laws and to suspend habeas corpus, if necessary, to enforce the act.
While the Force acts and the publicity generated by the joint committee temporarily helped put an end to the violence and intimidation, the end of formal Reconstruction in 1877 allowed for a return of largescale disenfranchisement of African Americans.