Here you can see segregation in action with a time lapse of the Red line in Chicago:
And how do things get to be so racially segregated? Well, it comes from many factors (notably redlining and other intentionally racist actions), but one that cannot be ignored is a criminal justice system that to this day still views having a particular skin tone in a particular neighborhood sufficient grounds for a criminal investigation. And again, such systemic racism is that fault of many factors, but an obvious one is how openly racist, sexist, and xenophobic many police are and how little discipline is ever handed down to them as a result.
Finally, lest you be called out for trying to stop any of these problems, here's a handy guide on how to be an actual Reverse Racist ("reverse" because racism is supposed to happen to a certain kind of people).