This is an undisputed fact, as people in those communities will readily protest the "crime train" coming through their neighborhoods.[1][2]
[1]: http://lewwaters.com/2012/05/22/light-rail-likely-to-raise-v...
[2]: http://larslarson.com/would-you-trust-your-kid-on-the-crime-...
https://www.youtube.com/watch?v=81tihdzaecc
This is the same high school that has a huge active oil derrick in the middle of campus:
http://www.nileguide.com/destination/blog/los-angeles/2010/0...
That was the camel's nose under the tent, and organizations influenced by the Ku Klux Klan used zoning laws as a tool for enforcing segregation at a municipal level.
Zoning has been leaving its dirty mark since the 1920s.
Nowadays, you can probably just mentally substitute "colored" wherever you see "multi-family" or "high density", to get a sense of the original wording of the laws. The zoning map for my municipality actually uses the color brown for multi-family residential zones, and a light peach color for single-family & detached residential!
That may be an unfortunate coincidence. Zoning is probably much more about class boundaries than race now. Rich people don't want poor people walking past their houses. Or driving past them. Or seeing them. Or knowing they exist.