What does the Valley of Ashes symbolize in The Great Gatsby by Fitzgerald?

The Valley of Ashes, which is the dumping ground of industrial waste, represents a moral wasteland.

This valley, hidden between the city of New York and West and East Eggs, symbolizes the moral decay of the nouveau-riche, who indulge themselves in material pleasures with no regard for others or anything else that interferes with this enjoyment.

Furthermore, the valley of waste and corruption is "bounded on one side by a small foul river." This polluted river represents, too, the moral pollution of the souls of the reckless, "careless people" such as Tom Buchanan, who exploits other people, like George Wilson, as well as his wife Daisy, who recklessly wastes the life of Myrtle Wilson.

In addition, the Valley of Ashes signifies the "dead end" in which its residents live. For instance, Wilson himself has lost vitality from residing in the moral wasteland. Described as "a spiritless man" who is anemic and moves around with "white ashen dust" covering his pale hair and clothes, he holds the desperate hope that Buchanan will make a business deal with him that will elevate his condition some. Likewise, his wife Myrtle becomes the mistress of Tom in the hopes that he will bring her joy and take her out of this death-invoking valley where men crumble just as the industrial waste turns to ashes.