Mark Twain Image source: Library of Congress Mark Twain was the pen-name of American author Samuel Clemens who wrote of Tom Sawyer and Huckleberry Finn. Quotes by Mark Twain in Time OneIt ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so. More about Mark Twain Biography.com “Mark Twain in His Times” Wikiquote Michael Turner Conway Twitty