In the immediate post-Civil War era, political pressure in the North by the "Radical" Republicans called for a full abolition of slavery. With the southern states not yet having their voting power back, this resulted in the passage of the 13th, 14th and 15th amendments which, at least in theory, abolished slavery, and gave African-Americans and other minorities full equality before the law as well as voting rights. The federal government also kept troops in the South to protect these newly won freedoms and rights.
The victory was painfully short. Race riots and other forms of extreme violence against African-Americans, and whites who supported them began almost immediately. By 1877 there was no longer any political will in the North to enforce the law in the South. While slavery remained abolished, the "Black Codes" and segregation laws came into effect at the state level that erased the freedoms supposedly won by the 14th and 15th amendments. Essentially most African-Americans went from being slaves to a state of peonage known as sharecropping, and were gradually removed from the voting process due to poll taxes and other innovations in legal technicalities.
During this time the federal government also began a much expanded effort to remove Native Americans from western lands that included many massacres. General William Sherman's words summed up the deadly policy of US forces in 1866: "At least 10 Indians are to be killed for each white life lost. You should not allow the troops to settle down on the defensive but carry the war to the Indian camps, where the women and children are...[You] should not delay the punishment of the Indians as a people."
A rising tide of violence also targeted Asian immigrants, mostly in the West. By the end of this period a reversal of the small movement toward racial equality had indeed occurred as the values of white supremacy carried the day in setting the tone of race relations throughout the country.