After a newspaper reporter arrives at Gatsby’s mansion to try to interview him, the novel flashes back to tell the story of Gatsby’s past:
James Gatz—that was really, or at least legally, his name. He had changed it at the age of seventeen and at the specific moment that witnessed the beginning of his career [...]
So he invented just the sort of Jay Gatsby that a seventeen-year-old boy would be likely to invent, and to this conception he was faithful to the end.
This shift in the narrative reveals that James Gatsby is an “invented” identity; the titular “great” Gatsby is someone James Gatz created and dedicated himself to becoming when he was 17. By immersing the reader in this snapshot of Gatsby’s past, it becomes clear that Gatsby is perhaps not the mysterious spectacle that his many acquaintances gossip about—rather, he is an ordinary man from humble roots who has built his life around a false persona.
Indeed, the flashback goes on to tell James Gatz’s rather unremarkable backstory: he grew up on a farm in North Dakota, worked as a clam-digger and salmon-fisher on Lake Superior, and attended St. Olaf College for two weeks before dropping out. His life changed, though, when he worked as a “steward, mate, skipper, secretary, and even jailor” for a wealthy yachter and precious metals expert named Dan Cody. This experience, Nick explains, is what transformed James Gatz into James Gatsby:
To the young Gatz, resting on his oars and looking up at the railed deck, the yacht represented all the beauty and glamour in the world. I suppose he smiled at Cody—he had probably discovered that people liked him when he smiled.
Working on Cody’s yacht is what first exposed Gatz to the “beauty and glamour” that he went on to idolize and dedicate his life to pursuing, and it was also what taught Gatz that he could charm other people with his looks and personality—so much so that Cody left Gatz a $25,000 inheritance when he died. Gatz never received the inheritance money, but his time working under Cody nonetheless shaped him into the Jay Gatsby that Nick and the other characters know. All in all, then, this flashback gives the reader insight into Gatsby’s background that they wouldn’t otherwise get, making it clear that Gatsby is an entirely self-made man, both in terms of his wealth and his very identity.
The morning after Gatsby hides in the bushes outside Tom and Daisy’s house, watching the couple have dinner, the narrative flashes back as Gatsby tells Nick about his and Daisy’s past relationship:
[Daisy] was the first “nice” girl [Gatsby] had ever known. In various unrevealed capacities he had come in contact with such people, but always with indiscernible barbed wire between. He found her excitingly desirable. He went to her house, at first with other officers from Camp Taylor, then alone. It amazed him—he had never been in such a beautiful house before. But what gave it an air of breathless intensity, was that Daisy lived there—it was as casual a thing to her as his tent out at camp was to him.
By using a flashback to tell the story of when Gatsby first met Daisy in Louisville, the book draws connections between the experiences and emotions Gatsby had at this time and the person he has since become. From this flashback, it becomes clear that Gatsby thought of Daisy’s large, “beautiful” house as an extension of her: “what gave it an air of breathless intensity, was that Daisy lived there.” So, as he became infatuated with her, he also became infatuated with the opulence that surrounded her.
This flashback gives Nick (and the reader) insight into why Gatsby amassed his fortune, even though he isn’t genuinely interested in the fancy things he owns or the lavish parties he throws. It’s implied that Gatsby bought his mansion—which is located directly across the bay from Daisy and Tom’s mansion—because he associates “beautiful” houses with Daisy, and he has shaped his entire lifestyle around impressing Daisy, winning her back, and rekindling their past romance. Later in this flashback, Gatsby is “overwhelmingly aware of the youth and mystery that wealth imprisons and preserves,” which further suggests that he sees his wealth as a way of “preserving” the youthful years that he longs to recreate.
The flashback goes on to recount Gatsby’s return from WWI, when Tom and Daisy were newly married:
[Gatsby] came back from France when Tom and Daisy were still on their wedding trip, and made a miserable but irresistible journey to Louisville on the last of his army pay. He stayed there a week, walking the streets where their footsteps had clicked together through the November night and revisiting the out-of-the-way places to which they had driven in her white car. Just as Daisy’s house had always seemed to him more mysterious and gay than other houses, so his idea of the city itself, even though she was gone from it, was pervaded with a melancholy beauty.
Again, by shifting the narrative to the past, the reader is able to portray the way Gatsby felt at this time and how this experience shaped his character. Gatsby’s “miserable but irresistible” trip to Louisville and the city’s “melancholy beauty” reflect his complicated relationship with Daisy—he is entirely consumed with the idea of her, even though this fixation makes him “miserable” and self-destructive. Moreover, the idea that his feelings for Daisy color his experience of the city further develops the idea that Gatsby’s yearning for Daisy is what motivated him to create his titular “great” person after the events of this flashback—his feelings for her have “pervaded” everything he’s done, influencing all of his decisions and shaping his very identity.