McDonalds!  By a long shot.  However, second place goes to a new name.

Wendy's passed Burger King last year to becoe the nation's second biggest hamburger chain for the first time since it was founded in 1969.  (I was also founded in 1969!)  Wendy's had sales of $8.5 billion, compared to $8.4 billion for Burger King.  McDonald's sales was a whopping $34.2 billion.