F. Scott Fitzgerald coined the term "Jazz Age" to describe the decade of decadence and prosperity that America enjoyed in the 1920s, which was also known as the Roaring Twenties. After World War I ended in 1918, the United States and much of the rest of the world experienced an enormous economic expansion. The surging economy turned the 1920s into a time of easy money, hard drinking (despite the Prohibition amendment to the Constitution), and lavish parties. Though the 1920s were a time of great optimism, Fitzgerald portrays the much bleaker side of the revelry by focusing on its indulgence, hypocrisy, shallow recklessness, and its perilous—even fatal—consequences.
The American Dream—that hard work can lead one from rags to riches—has been a core facet of American identity since its inception. Settlers came west to America from Europe seeking wealth and freedom. The pioneers headed west for the same reason. The Great Gatsby shows the tide turning east, as hordes flock to New York City seeking stock market fortunes. The Great Gatsby portrays this shift as a symbol of the American Dream's corruption. It's no longer a vision of building a life; it's just about getting rich.
Gatsby symbolizes both the corrupted Dream and the original uncorrupted Dream. He sees wealth as the solution to his problems, pursues money via shady schemes, and reinvents himself so much that he becomes hollow, disconnected from his past. Yet Gatsby's corrupt dream of wealth is motivated by an incorruptible love for Daisy. Gatsby's failure does not prove the folly of the American Dream—rather it proves the folly of short-cutting that dream by allowing corruption and materialism to prevail over hard work, integrity, and real love. And the dream of love that remains at Gatsby's core condemns nearly every other character in the novel, all of whom are empty beyond just their lust for money.
The Great Gatsby portrays three different social classes: "old money" (Tom and Daisy Buchanan); "new money" (Gatsby); and a class that might be called "no money" (George and Myrtle Wilson). "Old money" families have fortunes dating from the 19th century or before, have built up powerful and influential social connections, and tend to hide their wealth and superiority behind a veneer of civility. The "new money" class made their fortunes in the 1920s boom and therefore have no social connections and tend to overcompensate for this lack with lavish displays of wealth.
The Great Gatsby shows the newly developing class rivalry between "old" and "new" money in the struggle between Gatsby and Tom over Daisy. As usual, the "no money" class gets overlooked by the struggle at the top, leaving middle and lower class people like George Wilson forgotten or ignored.
Nick and Gatsby are continually troubled by time—the past haunts Gatsby and the future weighs down on Nick. When Nick tells Gatsby that you can't repeat the past, Gatsby says "Why of course you can!" Gatsby has dedicated his entire life to recapturing a golden, perfect past with Daisy. Gatsby believes that money can recreate the past. Fitzgerald describes Gatsby as "overwhelmingly aware of the youth and mystery that wealth imprisons and preserves." But Gatsby mixes up "youth and mystery" with history; he thinks a single glorious month of love with Daisy can compete with the years and experiences she has shared with Tom. Just as "new money" is money without social connection, Gatsby's connection to Daisy exists outside of history.
Nick's fear of the future foreshadows the economic bust that plunged the country into depression and ended the Roaring Twenties in 1929. The day Gatsby and Tom argue at the Plaza Hotel, Nick suddenly realizes that it's his thirtieth birthday. He thinks of the new decade before him as a "portentous menacing road," and clearly sees in the struggle between old and new money the end of an era and the destruction of both types of wealth.