Racial segregation existed throughout the United States, North, and South. As one historian of segregation has written, "no reflective historian any longer believes" that Northern states were innocent of the historical crimes of slavery and later segregation. By the twentieth century, Jim Crow laws were not generally on the books of Northern states and cities (though they had been in the nineteenth century.) Nor were racial attitudes as hardened in Northern states as in the Jim Crow South. But segregation, and the racist assumptions that undergirded it, existed north of the Mason-Dixon line too. The difference between segregation in the two regions is usually summarized as "de facto" versus "de jure." Southern racial hierarchies were in fact rigidly enforced by laws that established inflexible boundaries, intended not just to segregate but to establish and maintain white supremacy. In Northern cities in particular, though, segregation was enforced by other means. Neighborhoods, particularly the suburbs that boomed after World War II, established "restrictive covenants" that forbade property owners from selling to African American families. The famous Levittown developments, for example, remained accessible to whites only well into the 1960s due to such agreements. The federal government "redlined" minority neighborhoods, denying government-insured loans to individuals who lived in these areas irrespective of their credit-worthiness. School district lines were drawn in order to establish "neighborhood" schools that were very often highly segregated, and as the infamous riots that gripped Boston in response to busing measures in 1974 demonstrated, ordinary Northerners responded with violence to attempts to integrate neighborhoods and schools. Of course, racial segregation in the South was brutal and pervasive. But the underlying assumptions of white supremacy and the practices of racial segregation existed throughout the country, with perhaps equally insidious effects.

Racial segregation in the North differed from that in the South by being less acute, but both regions of the country practiced segregation.

The South reinforced segregation with more legislation against blacks, including laws that made it difficult for blacks to vote and change their situation, and also with the lynchings of black men. While some lynchings occurred in the North, they were were far less frequent.

Some housing developments in the North, such as the famous Levittowns in New York and Pennsylvania, which epitomized suburban development in the late 1940s and 1950s, were legally able to bar blacks from buying houses. Other neighborhoods had racist covenants in order to stay white only. Schools in the North were segregated, and even black celebrities could have a hard time finding a hotel room in some areas of the North.

States that were not part of the South during in Civil War in that they did not secede, such as Maryland, did not allow blacks and whites to marry until 1967, which acted to segregate the races.

Racism did not suddenly disappear in the United States when blacks crossed the Mason-Dixon line or moved into a non-Confederate state. Blacks might have had an easier time in the North than the South, but the North was still no picnic.

Legislation passed in the 1960s, such as Fair Housing Act of 1968, made it illegal to discriminate against people on the basis of race. However, red-lining, in which blacks and whites are steered into different neighborhoods, still occurs to this day.

There are two types of segregation practiced against the African Americans in the North and South, namely de jure and de facto. De jure segregation involved the use of laws to enforce segregation policies, while in de facto segregation, the law was not used to enforce segregation policies but segregation still existed. In the South, de jure segregation was practiced whereby both the police and the legal system enforced segregation. The infamous Jim Crow laws ensured racial segregation in virtually all spheres of public life including education, voting, and transportation, among others. Even though such laws were absent in the North, racial discrimination was still present in almost all aspects of life including housing, employment, and education. The unending suffering sustained by the Jim Crow laws eventually led to the formation of the Civil Rights Movements to fight for equal rights and treatment for African Americans. Eventually, these laws were overturned by landmark court rulings like Brown v Board of Education, in which the Supreme Court outlawed segregation in schools.

The major difference between segregation in these two regions is that segregation in the North was de factowhile segregation in the South was de jure.

In the North, there was not much segregation of public facilities (like busses) as there was in the South.  But there was (and is) a great deal of residential segregation.  This segregation was not caused by law.  Instead, it was caused by things like real estate agents steering blacks into black neighborhoods and landlords refusing to rent apartments in white areas to black people.  Through such informal methods, segregation was maintained in many cities in the North even though there were no laws requiring it.