Nick Carraway, the story's narrator, has a singular place within The Great Gatsby. First, he is both narrator and participant. Part of Fitzgerald's skill in The Great Gatsby shines through the way he cleverly makes Nick a focal point of the action, while simultaneously allowing him to remain sufficiently in the background. In addition, Nick has the distinct honor of being the only character who changes substantially from the story's beginning to its end. Nick, although he initially seems outside the action, slowly moves to the forefront, becoming an important vehicle for the novel's messages.
On one level, Nick is Fitzgerald's Everyman, yet in many ways he is much more. He comes from a fairly nondescript background. He hails from the upper Midwest (Minnesota or Wisconsin) and has supposedly been raised on stereotypical Midwestern values (hard work, perseverance, justice, and so on). He is a little more complex than that, however. His family, although descended from the "Dukes of Buccleuch," really started when Nick's grandfather's brother came to the U.S. in 1851. By the time the story takes place, the Carraways have only been in this country for a little over seventy years — not long, in the great scope of things. In addition, the family patriarch didn't exhibit the good Midwestern values Nick sees in himself. When the civil war began, Nick's relative "sent a substitute" to fight for him, while he started the family business. This little detail divulges a few things: It places the Carraways in a particular class (because only the wealthy could afford to send a substitute to fight) and suggests that the early Carraways were more tied to commerce than justice. Nick's relative apparently doesn't have any qualms about sending a poorer man off to be killed in his stead. Given this background, it is interesting that Nick would come to be regarded as a level-headed and caring man, enough of a dreamer to set goals, but practical enough to know when to abandon his dreams.
Also contributing to Nick's characterization as an Everyman are his goals in life. He heads East after World War I, seeking largely to escape the monotony he perceives to permeate the Midwest and to make his fortune. He is an educated man who desires more out of life than the quiet Midwest can deliver (although it is interesting that before living in the city any length of time he retreats to the country). What helps make Nick so remarkable, however, is the way that he has aspirations without being taken in — to move with the socialites, for example, but not allowing himself to become blinded by the glitz that characterizes their lifestyle. When he realizes what his social superiors are really like (shallow, hollow, uncaring, and self-serving), he is disgusted and, rather than continuing to cater to them, he distances himself. In effect, motivated by his conscience, Nick commits social suicide by forcefully pulling away from people like the Buchanans and Jordan Baker.
In addition to his Everyman quality, Nick's moral sense helps to set him apart from all the other characters. From the first time he interacts with others (Daisy, Tom, and Jordan in Chapter 1), he clearly isn't like them. He is set off as being more practical and down-to-earth than other characters. This essence is again brought to life in Chapter 2 when he doesn't quite know how to respond to being introduced into Tom and Myrtle's secret world (notice, however, that he doesn't feel the need to tell anyone about his adventures).
In Chapter 3, again Nick comes off as less mercenary than everyone else in the book as he waits for an invitation to attend one of Gatsby's parties, and then when he does, he takes the time to seek out his host. From these instances (and others like them spread throughout the book) it becomes clear that Nick, in many ways, is an outsider.
Nick has what many of the other characters lack — personal integrity — and his sense of right and wrong helps to elevate him above the others. He alone is repulsed by the phony nature of the socialites. He alone is moved by Gatsby's death. When the other characters scatter to the wind after Gatsby's death, Nick, unable to believe that none of Gatsby's associates will even pay their last respects, picks up the pieces and ensures Gatsby isn't alone in his death. Through the course of The Great Gatsby Nick grows, from a man dreaming of a fortune, to a man who knows only too well what misery a fortune can bring.