Extensive system of state and federal highways developed in 1950’s and 60’s.  Urbanization has always followed transportation routes – first suburbanization occurred in early-1800’s as railroads and streetcar lines were built from central city to outskirts of city.

People cited public service reasons, neighborhood reasons, and reasons specific to their house

Some things that are specific to people’s preferences (e.g. wanting a newer home, economic characteristics of neighborhood), but also many things that are determined by local gov – and therefore are changeable – schools, public services.