The fears are/were that the natural beauty of certain types of development would be spoiled by low-income housing, factories, and commerce. Of course, as you say, it's very any I - market. People already tend to naturally cluster based on income, level of education, desire for public goods, etc, so it shouldn't be necessary to have such restrictions.
It inevitably comes down to money, too, where minimum lot size restrictions shut out potential tenants/owners who can afford the per square foot cost in low quantities but not a large property. These restrictions are supposed to ensure a high enough tax yield per dwelling, but it's in the name of beautification.
You could say it all goes back to the car. When it suddenly became much cheaper for low income people to move out of the city center and commute from traditionally rich suburban areas, the rich got scared. Some moved further away, but governments also used zoning laws to make sure to poor stayed in the city, where they belonged.
You can't understand American city structure without the context of race relations here.
Hoping to evoke a Keystone Cops-on-a-map style mental image.
Didn't mean the phrasing literally, as much as in parody. That said, there is an element of upwardly mobile African Americans seeking opportunities for their children. While they are not explicitly "chasing white people", this search frequently lands them in the same suburban locales.
- https://en.wikipedia.org/wiki/Zoning#Functional_zoning_-_cat...
- https://en.wikipedia.org/wiki/Zoning#Criticism_of_zoning_law...
Then that Wikipedia article needs to be amended.
Look at an example from the real world. This is happening right now, in Portland Oregon. http://www.portlandmercury.com/portland/two-portland-glass-c...
The problem is that glass factories are "adjacent to a 100-child daycare facility, two public schools (Cleveland High School and Winterhaven K-8), and a city park."
These factories have been emitting metals such as cadmium and arsenic into the air. As you can imagine, this being Portland, everyone is quite upset. And rightly so.
You can argue about the quantities of emission that any given plant should be allowed. But you can't argue that, for any given emission level, society as a whole is much better off if these factories aren't adjacent to daycare facilities and schools.
Keeping schools and factories separated is a very legitimate "safety" goal of zoning.
Really, look at satellite photos of a modern American city and it's primarily car infrastructure.
http://humantransit.org/2013/05/how-sim-city-greenwashes-par...
http://usa.streetsblog.org/2014/04/10/parking-craters-arent-...
That's what Americans do with the free market.
You don't know the half of it.
Suburban sprawl was national policy during the Cold War. The idea was to spread out the population to reduce the damage a nuclear weapon could do.
They did it on purpose.
This happened because the native populations of the USA were far less technologically developed and highly-reproductive until ~18th Century when they got displaced.