This is really complex questions but I will try to keep my answer tight. After the end of the Civil War former slave owners' were crushed by southern economic downturn. Before the war, most southern planters' wealth was dependent on their slaves and land. After the war, the federal government declared the Confederate dollar worthless and the planters lost their slaves without compensation.

Given these financial issues, planters needed a docile labor force willing or forced to work for low wages. Employers were convinced that African Americans would not work without being forced to by stringent vagrancy laws, restrictive labor contracts, and the threat of violence.

Former slave owners wanted to rule over their employees with the same authority they had exercised over their slaves. they accepted the demise of slavery, they could not accept a world in which African Americans would have the same rights as whites. As a result, employers would reacted violently to any challenge to their dominance. One Mississippi newspaper, summarized the attitude of most former slave owners, "The true station of the negro is that of a servant. The wants and state of our country demand that he should remain a servant."

These laws were called Black Codes and these laws only applied to African Americans, which were designed to restrict freed Black peoples’ activity and ensure their availability as a labor force. These laws did offer some legal rights on former slaves, such as the right to enter into legal contracts. as in, the right to marry and acquire personal property. far More significant though, the Black Codes limited African Americans' lives. In Mississippi for example, they passed laws, that prohibiting African Americans from possessing guns and leasing or renting land in rural areas. Some Black Codes also forbade interracial marriages, and others stated that could not testify against a white person, or prohibited African Americans from serving on juries.

Along with the passage of the Black Codes, labor contracts and sharecropping, white vigilante groups and secret organizations sprang up throughout the South to terrorize African Americans and keep them from exercising their vision as free people and keep them dependent on whites. The best-known of these organizations was the Ku Klux Klan, besides violence aimed at keeping African-American men from voting, Southern whites also refused to rent them land or give them credit or jobs if they supported the Republican party.

During this time in the 1870s, Northern commitment to Reconstruction continued to wane. Northern whites wearied of the turmoil of Reconstruction. Many began to believe that peace would occur only if the Southern whites controlled Southern state governments and African Americans, completely understanding this meant that white domination would subvert the idea of equal rights. After 1872 election, the federal government became increasingly unwilling to use federal troops to stop violence against African-American voters and lawmakers. Also in 1872, Congress gave back the right to vote to most Confederate supporters, as a result of whites voting once more, the desertion of some Southern whites from the Republican party, and the disenfranchisement of some African-American through through violence and other means, more Democrats were elected and took control of state governments in the South. These legislators enacted various methods of keeping blacks from voting. Along with moving polling places into white areas and providing fewer ones where African Americans lived, they also passed poll taxes and established property qualifications for voting. African Americans who could not afford to pay the poll tax could not vote. As a result, fewer African American lawmakers were elected.

In 1876, the federal government completely withdrew even its marginal support for Reconstruction. In the presidential election of that year, the Democratic candidate, Samuel J. Tilden, won the popular vote over the Republican nominee, Rutherford B. Hayes. Because in some states, particularly in the South, the votes were contested with both parties declaring victory, Tilden did not gain the needed electoral college votes. So in 1877 Congress worked out a compromise that decided in favor of Hayes by one vote. Meanwhile, Republican and Democratic leaders informally decided that if Southern congressmen would accept Hayes, he would withdraw federal troops from the South. Such a policy. would one again allow white Southerners to disenfranchise Southern black men this time without federal interference.

This led to a 100 plus years Jim Crow, segregation, violence and lynching against African Americans. Of course this is the cliff notes version so let me know if you have any questions

Sources:

To Make Our World Anew_ Volume II_ A History of African Americans Since 1880 by Robin D. G. Kelley, Earl Lewis