In consideration of Gatsby's rise and fall, the emphasis on geography, the billboard of Dr. T.J. Eckleberg, and the behavior of the secondary...

It seems as though Fitzgerald is saying that the American Dream, the belief that a person can pull himself up by his bootstraps to achieve affluence and status simply through hard work, is a fiction in the American 1920s.  This is the very dream that Gatsby has: he wants the money, the life, the status, and the girl.  He comes from a working-class family and through discipline (consider his childhood schedule), meeting the right people...

It seems as though Fitzgerald is saying that the American Dream, the belief that a person can pull himself up by his bootstraps to achieve affluence and status simply through hard work, is a fiction in the American 1920s.  This is the very dream that Gatsby has: he wants the money, the life, the status, and the girl.  He comes from a working-class family and through discipline (consider his childhood schedule), meeting the right people (Dan Cody), and hard work (albeit illegal), he gets the money and the life, but he cannot acquire status or ultimately win the "golden girl."  Money simply isn't enough to change one's status or to be accepted by the old money.

The peculiar geography of Long Island would seem to confirm this inability to really change one's stripes as well.  No matter how hard she tries, Myrtle cannot escape the valley of ashes.  No matter how hard he tries, Gatsby cannot be accepted by East Eggers.  When Daisy and Tom come to one of Gatsby's parties in West Egg, Daisy doesn't like it; it seems gauche to her East Egg sensibilities.  George Wilson wants to get out of the valley of ashes and "go west," but he can't.  Everyone remains, eventually, trapped in their place, and the places -- symbolically -- connote status.  Even the decrepit billboard for Dr. T.J. Eckleberg and its position in the valley of ashes could indicate that it was ineffectual at drumming up the business it was intended to.  Perhaps his business has since gone under since he paid for the advertisement; one would assume that, had it been effective, it would be kept up. 

All of these circumstances would seem to confirm that it is ultimately impossible for a person to change their status in the 1920s in America.  One might go from poor to rich but one can never go from a low status to a high one; therefore, the American Dream is really not possible.