Almost thirty years old, Nick seems only recently to have decided what to do with his life when he comes East. He explains that he graduated from Yale in 1915. There's an unexplained gap between that and leaving to fight in World War I, which the US did not get involved in until 1917. After the war, he comes back to his home near Chicago, and for a few years he doesn't seem to be able to get his footing. He finds himself particularly restless in the Midwest and wants to get away.

After consulting with this family, Nick comes East to learn and start a career in the bond business. He is born to a wealthy family that owns hardware stores, so his father can finance him for a year in this venture.

Nick doesn't tell us everything. He doesn't tell us what careers he might have tried and abandoned at a time when most young men were well established in a vocation by age thirty. He also doesn't mention what Daisy and Tom will bring up when he comes to dinner at their home: they think he is engaged to marry a woman out West, having heard a rumor. This he vehemently denies, but he later ruminates that he has to break it off with this woman to whom he's still signing his letters "love." Reading between the lines, we can infer that extricating himself from this relationship is another factor driving his "restless" behavior.

After returning from the First World War, Nick Carraway, like so many young men of his generation, feels more than a little restless. Once upon a time, his native Midwest was the “warm center of the world” but no longer. Now it feels like “the ragged edge of the universe.”

So Nick decides to head out East to learn the bond business. “Everybody [he knows is] in the bond business, so [he supposes] it could support one more single man.”

Nick's decision precipitates a lively discussion among his family. His aunts and uncles talk about it as if they're choosing a prep school. Eventually, they come round to the idea, and Nick's father agrees to finance him for a year. And so Nick finally heads out East.

Nick's choice of career tells us a lot about America at that time. Right throughout the 1920s, the stock market kept on rising, regularly reaching new heights as more people than ever before began buying bonds and shares. For a lot of people, it seemed that the stock market was the high road to riches.

And so many young men—and all of those working in the bond business were men in those days—wanted to get in on the action by finding employment with Wall Street brokers in the hope of making phenomenal sums of money.

In the first chapter of the novel, Nick explains that after he graduated from college in 1915, he fought in the Great War (World War I). His explanation of what happened when he came home, however, is somewhat curious. He says,

I enjoyed the counter-raid so thoroughly that I came back restless. Instead of being the warm center of the world, the Middle West now seemed like the ragged edge of the universe—so I decided to go East and learn the bond business.

Seven years after he graduated from college and three years after the end of the war, Nick moved from the Midwest, his home, to New York City. However, the fact that he says that he "thoroughly enjoyed" any part of fighting in the largest scale war known to humankind at that stage in history is odd. So many people, soldiers especially, had their worldview completely reshaped as a result of this war. There was so much bloodshed, the result of new and more powerful weapons, that people became terribly disillusioned as a result.

So when Nick says that he thoroughly enjoyed the counter-raid, he is likely speaking euphemistically because he learned that the old adage is true: you can never go home again. He tried to return to the Midwest, his home, and he found that it no longer suited him. It didn't feel like a warm and comfortable home anymore; it seemed far away from everything, somehow insubstantial.So, where can one go that would feel vital and busy and important? New York City, he decides—specifically Wall Street, as Nick says,

Everybody I knew was in the bond business, so I supposed it could support one more single man.  

As Nick explains in chapter one, he moved East in order to start a new job and to experience a new llifestyle.  He had grown up in the Midwest, and he felt ready for a change.  A big cause of his feeling a need for a change was the fact that he had just returned from fighting in World War I.  As he explains:

I graduated from New Haven in 1915, just a quarter of a century after my father, and a little later I participated in that delayed Teutonic migration known as the Great War. I enjoyed the counter-raid so thoroughly that I came back restless. Instead of being the warm centre of the world, the Middle West now seemed like the ragged edge of the universe — so I decided to go East and learn the bond business.

Though his parents are not especially happy with his decision, his father agrees to finance him for a year.  This income, of course, is in addition to anything he can earn at his work.  As to why he chooses this particular type of work, he says:

Everybody I knew was in the bond business, so I supposed it could support one more single man.

Nick initially planned to live in New York City close to work, but "when a young man at the office suggested that (they) take a house together in a commuting town, it sounded like a great idea."  In this way, he ends up living next to Gatsby in West Egg.  The other man, however, ends up taking a job elsewhere, so Nick lives in his bungalow alone.

When Nick returns from the war, why does he decide to go East in The Great Gatsby?

As the previous post says, ostensibly it was to sell bonds on Wall Street and escape the known and predictable land of the midwest.

In a larger sense, it was obviously so that the story could happen.  The midwest was, as I said, predictable, honest, not intriguing.  The creation of Jay Gatsby needed the midwest as a place where the idea was born, but he couldn't reach out to the world and attempt to squeeze into the world he wanted to be a part of in the midwest.  So Nick had to move out east so that he could (and we by proxy could) meet Gatsby and tell the story.

It isn't all that different from our impression of the Midwest today.  It is a place where things are bound by tradition, values, things move more slowly, etc.  Though many of these are simply perceptions and impressions, again, the story couldn't have happened there in Fitzgerald's mind.

When Nick returns from the war, why does he decide to go East in The Great Gatsby?

You can find this in Chapter 1.

To me, there are two reasons why Nick comes East after the war.

In practical terms, he is coming to New York because he has decided to sell bonds for a living and New York is the center of American financial markets.

In more psychological terms, Nick has been changed by his experiences in the war.  He feels as if the Midwest is sort of like the middle of nowhere now that he has seen more of the world.  So he comes East because it seems more like someplace important and exciting.

You can see both reasons in this quote:

I came back restless. Instead of being the warm centre of the world, the Middle West now seemed like the ragged edge of the universe—so I decided to go East and learn the bond business.

In The Great Gatsby, why does Nick go East?

In the Great Gatsby, Nick, who's full name is Nick Carraway, is established as the narrator of the story at the beginning of the book. In chapter 1, the reasons why Nick decided to go East are established. Nick talks about his service in the Great War, and states on page 3 of chapter 1, that upon returning home, "the Middle West now seemed like the ragged edge of the universe." This quote illustrates to the reader that Nick now finds himself bored in the Mid-Western community where he grew up, and alludes to the fact that he feels life in the East will be more exciting. After this revelation, Nick states that he decided to go East to "learn the bond business." Later, at the end of chapter 1, Nick reveals that he also decided to travel east because of rumors of him possibly being engaged being spread around his family and the community. This is shown on page 19 of chapter 1 when he states "The fact that gossip had published the banns was one of the reasons I had come East." Hope this helps!

In The Great Gatsby, why did Nick go to the East?

Nick grew up in the Middle West, attended college in New Haven, and went to Europe as part of the American forces involved in World War I. When he returned from the war, he found "the Middle West now seemed like the ragged edge of the universe", so that a change of location seemed highly desirable.

In looking for a new location and a suitable occupation, Nick realized that "everybody I knew was in the bond business, so I supposed it could support one more single man." His family all agreed that this plan made sense and seemed a wise choice for Nick. Because the center of the bond and banking world in the United States at that time was located in New York City, it was a logical decision that this was Nick's destination.