Llewellyn Park is a place a few miles south of New York City in New Jersey. Although not the first ever suburb (i.e. smaller city whose existence depends on a large city), in many ways Llewellyn Park was one of the first outposts in America of the modern institution of Suburbia.
Starting in 1852, a drug magnate by the name of Llewellyn S Haskell started buying land in West Orange, New Jersey. He and eight partners bought land every year until 1856, when they owned four hundred acres on the south slope of a mountain. Haskell then began to look for someone to help him turn it into the idealized suburb.
Haskell himself quite liked to dabble in city planning. He had grown up in New Gloucester, Maine, and so was used to relatively pastoral surroundings, which he thought were certainly lacking in New York City. He was also a member of a religious cult of the day called the Perfectionists, who believed that righteous living could bring about the perfect existence on earth. These influences conspired to make Haskell favorable to rural surroundings in the city, since they were superior to urban according to the dominant ideals of the day. So when Frederick Law Olmsted was designing Central Park, he received a great deal of support, both financial and ideological, from Haskell.
Llewellyn Park had a similar purpose. It was only 13 miles from the city by rail, so it was a relatively short commute if you could afford it. He said that he intended to build "a retreat for a man to exercise his own rights and privileges" in a picturesque, pastoral surrounding outside the city on which Llewellyn Park's residents depended for their livelihood. To help him, Haskell hired the leading architect of the day and one of the most outspoken proponents for pastoral living, Alexander Jackson Davis.
The two worked so well together in designing the community that it's difficult to tell whose ideas are whose in retrospect. Haskell insisted on the primacy of natural beauty in his nascent suburb and Davis made sure that the thing would work. They made sure that the streets weren't straight so that they would seem more natural, and they named the streets things like "Tulip," "Mountain," and "Passive." Although curving streets may not seem all that revolutionary, there was no precedent for them in the American history of planned cities where the rational ideas of the enlightenment (and the straight streets they mandated) had been dominant for almost 200 years. Fences were also disallowed, since they would break up the natural beauty of the place.
Another totally unique aspect of the place was the "Ramble." It was a fifty acre undeveloped space central to the design of the community. The only modifications to its natural state were the walkways added along the mountain ridge and along the stream. Having something this natural in the midst of a settlement would have been unthinkable to the Puritans, who were so petrified of any undeveloped space at all.
Exclusiveness is usually cited as one of the main reasons for the more recent (that is, post-WW2) development of suburbs in this nation, and Llewellyn Park was no exception in that regard. The lots were about three acres and so were fairly expensive, and no factories, shops, slaughterhouses, or other industrial development was allowed. This prohibition was not only because of the industrial byproducts such as stench and smoke but also because of the more human byproducts, namely the poor employees of these establishments. There was also a gate house at the main entrance that bore the now familiar suburban warning, "Private Entrance. Do Not Enter."
All the trouble to which Haskell and Davis went did not go to waste. Their settlement was recieved with much fanfare and hailed as one of the most desirable places that anyone could ever live. In fact, Thomas Edison lived there for a great proportion of his life, and Alexander Davis picked this bucolic suburb out of all the things he had designed in which to live out his retirement. To this day, Llewellyn Park remains exclusive and (at least on a map) appears to retain its original suburban character, parked next to I-280 for easy transport into town but still rich and pastoral on its mountain. Many towns across America would spring up according to this same template a hundred years later, but Llewellyn Park remains the first piece of the suburbs, as we now know them, in America.
Sources: www.mapquest.com for the present-day situation and Kenneth Jackson's Crabgrass Frontier for the history.