Samuel Langhorne Clemens was welcomed into the world as the sixth child of John Marshall and Jane Lampton Clemens on 30 November 1835. John and Jane could never have imagined that their son Samuel would one day be known as Mark Twain - America's most famous literary icon. 

In 1839, the Clemens family moved 35 miles east to the town of Hannibal, a growing port city that lie along the banks of the Mississippi, Hannibal was a frequent stop for steam boats arriving by both day and night from St. Louis and New Orleans. Samuel was often indoors because of his poor health. However, by age nine, he seemed to recover from his weakness and joined the rest of the town's children outside. He then began attending a private school in Hannibal. When Samuel was 12, his father died of pneumonia, and at 13, Samuel left school to become a printer's apprentice. After two short years, he joined his brother Orion's newspaper as a printer and editorial assistant. It was here that young Samuel found he enjoyed writing. 

At 17, he left Hannibal and went to St. Louis looking for a printer's job. While he was staying there, he became a river pilot's apprentice and got his professional license in 1858. Clemens' pseudonym, Mark Twain, comes from his days as a river pilot. It is a river term which means two fathoms or 12-feet when the depth of water is enough for a boat to sail. "Mark twain" means that is safe to navigate. 

Clemens began working as a newspaper reporter for several newspapers all over the United States because the river trade was in a really bad situation when the Civil War in 1861. In 1870, Clemens married Olivia Langdon, and they had four children, one of whom died in infancy and two who died in their twenties. Their surviving child, Clara, lived to be 88, and had one daughter. Clara's daughter died without having any children, so there are no direct descendants of Samuel Clemens living. 

Mark Twain passed away on April 21, 1910, but he has got recognition still today. His childhood home is open to the public as a museum in Hannibal and in New York City, tours are offered to show around the places which Twain visited near his birthday every year.

Adapted from

http://www.cmgww.com/historic/twain/about/bio.htm