Samuel Langhorne Clemens grew up in Hannibal, Missouri, where he got some kind of education and was apprenticed to a printer. At various times, he was a steamboat pilot on the Mississippi River, a gold prospector, a journalist and an editor, before gaining fame and fortune with Tom Sawyer and other works.
The pen-name 'Mark Twain' is said to have been taken from a boatman's cry used on the Mississipi at the time.