Geography plays an important role in distinguishing persons of different social or economic classes in The Great Gatsby.
When Nick moves to Long Island, he comes to reside in West Egg, one of the two egg-shaped peninsulas on the island. Nick soon comes to understand that West Egg is "the less fashionable of the two," with a further disparity between Nick's "small eyesore" of a house and the Gatsby mansion next door. West Egg was the residence of the people who had "new money" or who aspired to appear as if they had new money.
East Egg, on the other hand, was the location for "the white palaces of fashionable East Egg," the homes of those with well-established and well-endowed financial and social standings. The Buchanans lived on East Egg.
Caught in the desolate divide between Long Island and New York City was the "valley of ashes," which was as gray and hopeless for its residents as it sounded. George and Myrtle Wilson were trapped in this place - trapped by the realities of George's business, trapped by the circumstances of their loveless marriage, trapped by their inability to improve their situation.