The Union victory in the Civil War in 1865 may have given some 4 million slaves their freedom, but the process of rebuilding the South during the Reconstruction period (1865-1877) introduced a new set of significant challenges. Under the administration of President Andrew Johnson in 1865 and 1866, new southern state legislatures passed restrictive “black codes” to control the labor and behavior of former slaves and other African Americans. Outrage in the North over these codes eroded support for the approach known as Presidential Reconstruction and led to the triumph of the more radical wing of the Republican Party. During Radical Reconstruction, which began in 1867, newly enfranchised blacks gained a voice in government for the first time in American history, winning election to southern state legislatures and even to the U.S. Congress. In less than a decade, however, reactionary forces–including the Ku Klux Klan–would reverse the changes wrought by Radical Reconstruction in a violent backlash that restored white supremacy in the South.