Reconstruction was primarily the work of the Radical Republicans in Congress, who controlled both the House of Representatives and the Senate during most of the Reconstruction era (1865-1877). They enacted a series of laws and amendments to the Constitution in order to rebuild the South and ensure the rights of former slaves. These laws and amendments included the Thirteenth Amendment, which abolished slavery; the Fourteenth Amendment, which guaranteed citizenship rights to all persons born or naturalized in the United States, including former slaves; and the Fifteenth Amendment, which prohibited states from denying the vote to citizens on the basis of race.