Samuel Langhorne Clemens, better known by his pen name Mark Twain, was an American writer, humorist, entrepreneur, publisher, and lecturer. He is best known for his novels The Adventures of Tom Sawyer and its sequel, Adventures of Huckleberry Finn, which are among the first great American novels. Twain was raised in Hannibal, Missouri, which provided the setting for Tom Sawyer and Huckleberry Finn. He served an apprenticeship with a printer and then worked as a typesetter, contributing articles to the newspaper of his older brother Orion Clemens. He later became a riverboat pilot on the Mississippi River before heading west to join Orion in Nevada. He referred humorously to himself as 'Mark Twain, ' which was a call used by riverboat workers when measuring the depth of water.