On December 18, 1865, the 13th Amendment was adopted as part of the United States Constitution. The amendment officially abolished slavery, and immediately freed more than 100,000 enslaved people, from Kentucky to Delaware. The language used in the 13th Amendment was taken from the 1787 Northwest Ordinance.

Yet the 13th Amendment maintains an important exception for keeping people in "involuntary servitude" as "punishment for crime whereof the party shall have been duly convicted." Some scholars say this exception ended slavery in one form only to allow it to continue in another. These laws are sometimes credited with laying the groundwork for the U.S. system of mass incarceration, which disproportionately imprisons Black people.

Two years earlier, at the height of the U.S. Civil War, President Abraham Lincoln issued the Emancipation Proclamation, which declared all Blacks held captive in the states who'd rebelled against the United States (as members of the Confederacy) were free. This did not have a sweeping practical impact, however, as the Confederacy considered itself a separate nation and did not follow U.S. laws, and the proclamation did not free enslaved populations in the “border states” that sided with the United States.

Within five years, Congress passed the 14th and 15th Amendments. These amendments, among the most contested in courts today, established citizenship, equal protection, and voting rights for all male Americans, regardless of race. However, the same suffrage and protections would not be afforded to women of all races until over 50 years later, when Congress passed the 19th Amendment in 1919.

At the time, Black people held in slavery by Native Americans in Indian Territory (now the state of Oklahoma) largely remained in bondage. Different factions of various tribes alternatively sided with the Confederacy and the United States. Regardless of their position, the U.S. government treated the Cherokee, Chickasaw, Seminole, Creek, and Choctaw as allies of the Confederacy. These tribes signed the Treaty of 1866, which abolished slavery, to normalize relations with the U.S.