The segregation and disenfranchisement laws known as "Jim Crow" affected almost every aspect of daily life, mandating segregation of schools, parks, libraries, drinking fountains, restrooms, buses, trains and restaurants. "Whites Only" and "Colored" signs were constant reminders of the enforced racial order.
In legal theory, blacks received "separate but equal" treatment under the law—in actuality, public facilities for blacks were nearly always inferior to those for whites, when they existed at all. In addition, blacks were systematically denied the right to vote in most of the rural South through the selective application of literacy tests and other racially motivated criteria.
The Jim Crow system was upheld by local government officials and reinforced by acts of terror perpetrated by vigilantes. In 1896, the Supreme Court established the doctrine of separate but equal in Plessy v. Ferguson, after a black man in New Orleans attempted to sit in a whites-only railway car.
Transit was a core component of segregation in the South. Keeping whites and blacks from sitting together on a bus, train or trolley car might seem insignificant, but it was one more link in a system of segregation that had to be defended at all times—lest it collapse. Thus transit was a logical point of attack for the foes of segregation, in the courtroom and on the buses themselves.
It would take several decades of legal action and months of nonviolent direct action before these efforts achieved their intended result.