I googled that phrase, and here is the third site that comes up:
http://www.answers.com/topic/city-planning
Suburban Planning
Cities grew both upward and outward in the second half of the nineteenth century. Tall buildings, products of steel construction and the elevator, turned the old low-rise downtown into central business districts with concentrations of office buildings, department stores, theaters, and banks. Improvements in urban mass transit fed workers and customers to the new downtowns and allowed rapid fringe expansion along the main transportation routes. The new neighborhoods ranged from tracts of small "workingmen's cottages" and cheap row housing to elegantly landscaped "dormitory" suburbs for the upper crust.
The most common form of development was the "streetcar suburbs." These were usually subdivisions laid out as extensions of the city grid. The developer sold lots to individual owners or small builders. These neighborhoods were often protected by restrictive covenants in deeds that set minimum house values, prohibited commercial activities, and excluded African Americans or Asians. The U.S. Supreme Court declared such covenants unenforceable in Shelley v. Kramer (1948).
Romantic suburbs drew on the developing tradition of park planning associated with Frederick Law Olmsted, designer of Central Park (Manhattan), Prospect Park (Brooklyn, New York), Mount Royal Park (Montreal), and many others. Olmsted saw parks as a way to incorporate access to nature within the large city and therefore preferred large landscaped preserves to small playgrounds. Parks functioned as "the lungs of the city" and gave the urban population access to nature.
The development that established the model for the suburbs was Riverside, outside Chicago. Designed by Olmsted in 1869, it offered large lots, curving streets, park space, and a commercial core around a commuter rail station. The exclusive residential development or suburb, with tasteful provision of retail facilities, schools, and churches, flourished in the late nineteenth century (for example, Chestnut Hill and the "Main Line" suburbs of Philadelphia) and the early twentieth century (for example, Shaker Heights near Cleveland, Mariemont near Cincinnati, and the Country Club District of Kansas City).