| It doesn't stop|
at the water's edge
Suburban sprawl in the United States is the inevitable result of the post-World War II doctrines of community planning that dictated building extensive tracts of low-density housing and a fairly strict segregation of development into commercial, residential, and industrial zones of various sorts. Originally a symbol of postwar prosperity (as well as white flight out of the cities), by the 1970s much suburban development had come to be seen in environmentalist and leftist circles as just as much blight as the urban poverty left behind.
This sprawl was encouraged by the twin post-war "opportunities" of cheap steel (with which to build cars) and cheap oil. It built on a quasi-rural lifestyle myth very common with Americans -- the desire to live on and in "the land", to have a nice leafy green backyard, and to have a nice chunk of property on which to own one's "castle".
The extensive development of suburban sprawl has been blamed for a lot of social ills, the greatest being the loss of the "walkable" community, confining residents to their cars for most activity and therefore reducing available opportunities for exercise, and the decay of downtown areas in favor of shopping malls and big box retail stores, often raising the barrier of entry for small food service and retail businesses in many areas. Public transportation is often inadequate or, more usually, entirely absent. Additionally, many such developments were built on what had formerly been farmland or open space. The wildfires of the last decade have particularly affected houses built on former forest land.
Proposals have been floated for solving some of the problems of suburban sprawl, but apart from a few recent attempts to restore some kind of mixed-use zoning to most suburban areas, most of them involve tweaking traffic flows and attempting to restore walkability. More extreme examples — Paolo Solieri's concept of the arcology, for example — have been floated, but are seldom taken seriously due to their impracticality and often-strained, or even false, assumptions about human nature.
The issue continues unresolved, especially in light of the late-2007/early-2008 mortgage crisis that left vast tracts of houses either foreclosed or unoccupied.