In the beginning of East of Eden, before introducing his characters, John Steinbeck carefully establishes the setting with a description of the Salinas Valley in Northern California. As a youngster, the narrator learns to tell east from the bright Gabilan Mountains and west from the dark Santa Lucias Mountains. The weather there is cyclic: years of heavy rainfall, then moderate rainfall followed inevitably by dryness which always surprises the inhabitants. Historically, the valley was settled first by "lazy" Indians, followed by the "greedy" Spanish and finally the "even greedier" Americans.
In 1870, the narrator's grandparents Samuel and Liza Hamilton immigrate from the north of Ireland and settle in the driest land in the Salinas Valley. Very prolific, they work hard to raise their nine children. Samuel's good nature and hard work on his near barren ranch makes him sympathetic to the reader. Liza is stern but good-hearted. Had their land been fertile, they would have been rich.
Samuel Hamilton is a neighbor of the wealthy Adam Trask but Adam settled in a much better part of the Salinas Valley after his move from New England. As a child in Connecticut, Adam lived with his devilish father Cyrus Trask-a one- legged syphilitic Civil War veteran-his affectionate stepmother Alice, who was a timid young woman intent on hiding her tuberculosis, and a cruel younger half-brother named Charles. His own mother commits suicide after learning Cyrus has infected her with syphilis. Cyrus creates a package of lies about his heroic role in the Civil War by studying military strategy and is so convincing that when he moves to Washington D.C. he is granted a very high government position.
Adam and Charles experience a difficult childhood. While Adam is gentle and passive, Charles' aggression becomes apparent when he beats his brother senseless after Adam defeats him for the first time in a game. Although Alice never smiles in public, Adam one day discovers his stepmother smiling by herself and secretly leaves her presents that she mistakenly believes are from her son Charles. Cyrus all the while attempts to convince Adam that the Army will make a man out of him, yet he doesn't encourage his other son Charles to join out of fear of exacerbating the dark parts of his personality. Charles feels deep resentment toward Cyrus for ignoring his birthday present, a valuable German knife, and for valuing instead the stray puppy given him by Adam. Jealousy overcomes Charles and he savagely beats his brother and leaves him close to death on the side of the road. Cyrus goes after Charles with a shotgun but in time settles down. While Adam is recuperating, Cyrus enlists him in the Army.
At the beginning, Steinbeck sets up the Biblical metaphor of good vs. evil, or light vs. dark by setting East of Eden in the Edenic splendor of the Salinas Valley, California, where he grew up. Evil is represented in the form of the Santa Lucias Mountains to the west and contrasted with light "good" welcoming Gabilan Mountains to the east. Although the narrator favored the light mountains, he nevertheless will, like all human beings, have to find his way through life's labyrinth of light and dark: good and evil.
Here, both the Hamilton and Trask families are introduced. Although the happy Hamilton family is fertile, ultimately containing nine children, they live on the poorest, driest most barren land. On the other hand, the Trask family, which lives on the richest most fertile land, is small and almost sterile. Samuel Hamilton and Cyrus Trask represent two biblical patriarchs, Samuel the archetypal force for goodness- loving, healthy, and passionate about education-and Cyrus, a force for evil-hateful, diseased and a liar. Samuel's brood will fare comparatively well, but the sins of the father will be visited upon the kind-hearted Adam and the evil-hearted Charles. Adam parallels the biblical shepherd Abel, whose sacrifice of his best lamb pleased God more than the farmer Cain's (the equivalent of Charles) offering of grain. This original incidence of sibling rivalry is mirrored throughout the novel.