John Jr. was born on February 27, 1902, in Salinas, California. He was of German, English, and Irish descent. Johann Adolf Großsteinbeck, Steinbeck's paternal grandfather, had shortened the family name to Steinbeck when he emigrated to the United States. The family farm in Heiligenhaus, Mettmann, North Rhine-Westphalia, Germany, is still today named "Großsteinbeck."
His father, John Ernst Steinbeck, served as Monterey County treasurer. John's mother, Olive Hamilton, a former school teacher, shared Steinbeck's passion for reading and writing. The Steinbecks were members of the Episcopal Church, although Steinbeck would later become agnostic. Steinbeck lived in a small rural town, no more than a frontier settlement, set in some of the world's most fertile land. He spent his summers working on nearby ranches and later with migrant workers on Spreckels sugar beet farms. There he became aware of the harsher aspects of migrant life and the darker side of human nature, which supplied him with material expressed in such works as Of Mice and Men. He also explored his surroundings, walking across local forests, fields, and farms. While working at Spreckels Sugar Company, he would sometimes work in their laboratory, which gave him time to write. He also had considerable mechanical aptitude and fondness for making his own repairs to things he owned.
Steinbeck graduated from Salinas High School in 1919 and went from there to study English Literature at Stanford University in Palo Alto, leaving, without a degree, in 1925. He travelled to New York City where he took odd jobs while trying to write. When he failed to have his work published, he returned to California and worked in 1928 as a tour guide and caretaker at Lake Tahoe, where he met Carol Henning, his first wife. The two were married in January 1930 in Los Angeles, where, with friends, he attempted to make money by manufacturing plaster mannequins.
When their money ran out six months later due to the market being slow, Steinbeck and Carol moved back to Pacific Grove, California, to a cottage owned by his father, on the Monterey Peninsula a few blocks outside the Monterey city limits. The elder Steinbecks gave John free housing, paper for his manuscripts, and from 1928, loans that allowed him to write without looking for work. During the Great Depression period, Steinbeck bought a small boat, and later claimed that he was able to live on the fish and crab that he gathered from the sea, as well as fresh vegetables from his garden and local farms. When that didn't work, Steinbeck and his wife were not above getting welfare, or rarely even stealing bacon from the local produce market. Whatever food they had, they would share with their friends. Carol became the model for Mary Talbot in Steinbeck's novel Cannery Row.
In 1930, Steinbeck met Ed Ricketts, who became a close friend and mentor to Steinbeck during the following decade, teaching him a great deal about philosophy and biology. Ricketts, usually very quiet, yet likable, with an inner self-sufficiency and an encyclopedic knowledge of diverse subjects, became a focus of Steinbeck's attention. Ricketts had taken a college class from Warder C. Allee, a biologist and ecological theorist, who would go on to write a classic early textbook on ecology. Ricketts became a proponent of ecological thinking, in which man was only one part of a great chain of being, caught in a web of life too large for him to control or understand. Meanwhile, Ricketts operated a biological lab on the coast of Monterey, selling biological samples of small animals, fish, rays, starfish, turtles, and other marine forms to schools and colleges.
Between the years 1930 to 1936, Steinbeck and Ricketts became close friends. Steinbeck's wife began working at the lab as secretary-bookkeeper. Steinbeck himself began helping out on an informal basis. They formed a common bond based on their love of music and art, and John learned biology and Ricketts' ecological philosophy. When Steinbeck became emotionally upset, Ricketts would sometimes play music for him.