Early life and education
Sinclair was born in Baltimore, Maryland, to Upton Beall Sinclair Sr. and Priscilla Harden Sinclair. His father was a liquor salesman whose alcoholism shadowed his son's childhood. Priscilla Harden Sinclair was a strict Episcopalian who disliked alcohol, tea, and coffee. Both of Upton Sinclair's parents were of English ancestry, and all of his ancestors emigrated to America from England during the late 1600s and early 1700s. As a child, Sinclair slept either on sofas or cross-ways on his parents' bed. When his father was out for the night, he would sleep alone in the bed with his mother. Sinclair did not get along with her when he became older because of her strict rules and refusal to allow him independence. Sinclair later told his son, David, that around Sinclair's 16th year, he decided not to have anything to do with his mother, staying away from her for 35 years because an argument would start if they met. His mother's family was very affluent: her parents were very prosperous in Baltimore, and her sister married a millionaire. Sinclair had wealthy maternal grandparents with whom he often stayed. This gave him insight into how both the rich and the poor lived during the late 19th century. Living in two social settings affected him and greatly influenced his books. Upton Beall Sinclair, Sr., was from a highly respected family in the South, but the family was financially ruined by the Civil War, disruptions of the labor system during the Reconstruction era, and an extended agricultural depression.
As he was growing up, Upton's family moved frequently, as his father was not successful in his career. He developed a love for reading when he was five years old. He read every book his mother owned for a deeper understanding of the world. He did not start school until he was 10 years old. He was deficient in math and worked hard to catch up quickly because of his embarrassment. In 1888, the Sinclair family moved to Queens, New York, where his father sold shoes. Upton entered the City College of New York five days before his 14th birthday, on September 15, 1892. He wrote jokes, dime novels, and magazine articles in boys' weekly and pulp magazines to pay for his tuition. With that income, he was able to move his parents to an apartment when he was seventeen years old.
He graduated in June 1897 and studied for a time at Columbia University. His major was law, but he was more interested in writing, and he learned several languages, including Spanish, German, and French. He paid the one-time enrollment fee to be able to learn a variety of things. He would sign up for a class and then later drop it. He again supported himself through college by writing boys' adventure stories and jokes. He also sold ideas to cartoonists. Using stenographers, he wrote up to 8,000 words of pulp fiction per day. His only complaint about his educational experience was that it failed to educate him about socialism. After leaving Columbia, he wrote four books in the next four years; they were commercially unsuccessful though critically well-received: King Midas (1901), Prince Hagen (1902), The Journal of Arthur Stirling (1903), and a Civil War novel titled Manassas (1904).
Upton became close with Reverend William Wilmerding Moir. Moir specialized in sexual abstinence and taught his beliefs to Sinclair. He was taught to "avoid the subject of sex." Sinclair was to report to Moir monthly regarding his abstinence. Despite their close relationship, Sinclair identified as agnostic.