After the Civil War, the South entered a period (lasting from 1865-1877) called Reconstruction, when the federal government oversaw the reconstruction of the government in Southern states.
Immediately after the war, a debate about how to recreate southern government and society was divided between Radical Republicans (mostly Northerners) who sought to enfranchise blacks and establish new political patterns, and Conservative Democrats (mostly Southerners) who wanted the federal government to step out and allow the south to rebuild itself as it saw fit. In 1866, Radical Republicans won the election, and created the Freedmen’s Bureau to offer former slaves food, clothing, and advice on labor contracts.
During Reconstruction, the Thirteenth, Fourteenth, and Fifteenth Amendments were passed in order to attempt to bring equality to blacks. Initially, with federal laws and federal troops offering protection, blacks bean to vote and gain political power. Soon after, Southern whites responded with violence and intimidation. Southern blacks soon lost their newfound freedoms. In 1877, because of expenses, administrative corruption, Northern exhaustion, and Southern protests, the federal government withdrew from the south, and black disenfranchisement and oppression quickly followed.