The Civil War and Reconstruction fundamentally changed the Constitution. The Thirteenth Amendment abolished slavery except as punishment for crime. The Fourteenth Amendment established birthright citizenship and promised equal protection of the laws. The Fifteenth Amendment sought to protect Black men's right to vote. For a brief period, the federal government enforced those constitutional guarantees, allowing formerly enslaved people to vote, hold public office, establish schools, reunite families, and begin building independent communities.

Those gains depended on continued federal enforcement. When that commitment ended, constitutional promises became increasingly meaningless for millions of Black Americans. The end of Reconstruction marked the beginning of a new legal order. American law once again became the principal tool for creating, legitimizing, and enforcing racial hierarchy.

Slavery could not legally return, but racial hierarchy could. Lawmakers, judges, and government officials built new legal systems that preserved white dominance without restoring slavery. Courts narrowed constitutional protections. Congress abandoned meaningful enforcement of civil rights. States and local governments enacted segregation laws, restricted voting, criminalized ordinary conduct, and enforced racial separation. White supremacist violence remained a constant, while law increasingly protected those responsible.

This legal order reached far beyond the South. Across the nation, governments used law to determine who could become a citizen, who could enter the country, who could own land, where people could live, what schools they could attend, what jobs they could hold, and who could participate fully in American democracy. Native Americans, Asian Americans, Latinos, immigrants, and African Americans faced different legal restrictions, but every rule reinforced the same racial hierarchy. During this period, courts also increasingly defined who counted as white. Whiteness became a legal status that carried citizenship, political power, economic opportunity, and social privilege.

Between 1878 and the end of World War II, American law rebuilt, expanded, and defended racial hierarchy. Through legislation, constitutional interpretation, judicial decisions, and administrative policies, governments at every level created a national legal system that subordinated African Americans while assigning every racial group a place within that hierarchy. The Civil Rights Movement would ultimately challenge not only the legacy of slavery, but the legal order that replaced it.