Mark Twain's real name was Samuel Langhorne Clemens. Before Clemens became well known as a writer, he held a variety of odd jobs including piloting a steamboat up and down the Mississippi River. He was licensed as a steamboat pilot in 1859 and worked on the river until fighting there during the Civil War ended traffic traveling from north to south. His experiences along the river helped him come up with his pen name. In 1863, when Clemens was 27, he wrote a humorous travel story and decided to sign his name "Mark Twain." This name comes from something shouted by crewmen (船员们) on a boat. To test the depth of the water, a crewman shouts "mark twain"! The crewman is calling for two fathoms (英寻), or a depth of 12 feet, which is barely enough for a boat to navigate safely. "Twain" is an old-fashioned way of saying "two" and a fathom is six feet. "Mark Twain" is a "pen name" in the same way that many people in show business use a "stage name." Samuel Clemens began his writing career as a reporter. He traveled all over the country recording stories he heard along the way. He went out west and visited mining camps and he went to San Francisco, where he sharpened his skill at ridiculing local officials for their incompetence, dishonesty and failure to help the citizens who most needed assistance. This kind of writing, humor alternating with serious fact, became Mark Twain's trademark style and made him and his pen name famous around the world.