Samuel Langhorne Clemens ( November 30 , 1835 -- April 21 , 1910 ) , more widely known as Mark Twain , was a well known American writer born in Florida , Missouri . Samuel Langhorne Clemens ( November 30 , 1835 â `` April 21 , 1910 ) , better known by his pen name Mark Twain , was an American author and humorist .