The practice of separating the races. It was common practice in the American South until the late 1960's to have separate bathrooms, water fountains, movie theaters, schools, etc. for whites and "coloreds", i.e. non-whites.
Although laws were passed (as well as Supreme Court decisions made) to outlaw segregation starting in the 50's, the federal government did little to enforce integration in the South until the issue was forced by civil rights activists.