Louis J. Budd, "Twain, Mark," American National Biography Online, February 2000, http://www.anb.org/articles/16/16-00313.html.
Samuel Clemens emerged from early frailty into a lively boyhood, though episodes of sleepwalking indicated strong tensions, probably increased by the deaths of a sister and then a brother. His parents, while apparently compatible, struck him as sharply different. His father, careful to come across as a gentleman, was a principled Whig and essentially a freethinker in theology who intimidated him, seeming stiff and austere; his mother, resilient, warm, comfortably religious, and playful, impressed him as a nonconformist. Hindsight cannot discover unusual promise (or lack of it), though his novels suggest that his boyhood involved much imaginative drama. Highly detailed reminiscences almost fifty years later proved that even casual events were embedded in his psyche. His distinctive way of processing experience was forming, and he remembered his surprise when his spontaneous opinions and phrasings first struck others as humorous. Boyhood ended before his twelfth birthday, when his father died. He attended school sporadically for two more years, took various odd jobs, and apprenticed with a printer, with whom he boarded. In 1851 he changed to typesetter and editorial assistant for his brother Orion's newspaper, which soon published his first known sketch. As his self-confidence rose, he placed a humorous yarn in a Boston periodical, already demonstrating the energetic ambition that drove his career despite the pose of laziness. His early writing showed instinctive exuberance, egalitarianism, irreverence, and boldness.