Population size matters to a degree, mostly because the larger the population, the higher the percentage of minorities, generally speaking. For a number of reasons, minority populations are higher in more urban areas. And greater numbers leads to more interracial exposure, which leads to a relatively higher degree of tolerance. It just happens that Chicago seems to have resisted full integration more than the other big cities. I used to live in Hyde Park, so I have seen first hand just how stark the contrasts within the city (and even a very small area) can be. I also spent time in NYC, and didn't get the same feeling, at least not to the extend I did in Chicago. In smaller cities, it is easier to shove the minorities off into a corner and ignore them, so to speak. then you haven't spent significant time in NYC. Chicago has the "city of neighborhoods" reputation that inevitably leads to different "sections". But NYC has the same thing. The dividing lines between the upper west/east sides and Harlem are stark. The areas of brooklyn are very strictly broken up. You take certain subway lines and it's mostly white people, others are mostly black and still others are made up of hispanic. What about LA? Nobody can tell me that's a highly integrated city.