Clemens was apprenticed to a printer at age 13 and later worked for his older brother, who established the Hannibal Journal. In 1857, the Keokuk Daily Post commissioned him to write a series of comic travel letters, but after writing five he decided to become a steamboat captain instead. He signed on as a pilot's apprentice in 1857 and received his pilot's license in 1859, when he was 23.
Clemens piloted boats for two years, until the Civil War halted steamboat traffic. During his time as a pilot, he picked up the term "Mark Twain," a boatman's call noting that the river was only two fathoms deep, the minimum depth for safe navigation. When Clemens returned to writing in 1861, working for the Virginia City Territorial Enterprise, he wrote a humorous travel letter signed by "Mark Twain" and continued to use the pseudonym for nearly 50 years.
In 1864, he moved to San Francisco to work as a reporter. There, he wrote the story that made him famous: The Celebrated Jumping Frog of Calaveras County.
In 1866, he traveled to Hawaii as a correspondent for the Sacramento Union. Next, he traveled the world writing accounts for papers in California and New York, which he later published the popular book The Innocents Abroad (1869). In 1870, Clemens married the daughter of a wealthy New York coal merchant and settled in Hartford, Connecticut, where he continued to write travel accounts and lecture. In 1875, his novel Tom Sawyer was published, followed by Life on the Mississippi (1883) and his masterpiece Huckleberry Finn (1885). Bad investments left Clemens bankrupt after the publication of Huckleberry Finn, but he won back his financial standing with his next three books--Pudd'Nhead Wilson (1894), Personal Recollections of Joan of Arc (1895), and Following the Equator (1897). In 1903, he and his family moved to Italy, where his wife died. Her death left him sad and bitter, and his work, while still humorous, grew distinctly darker. He died in 1910.