Who is John Galt? Billboard Sign

Who is John Galt? Billboard Sign - A biilboard sign was recently put up asking the question "Who is John Galt?" This is in reference to the book "Atlas Shrugged" written by Ayn Rand. Here is an article describing the sign in more detail. http://www.theusreport.com/the-us-report/i-95-john-galt-billboard-mystery-solved.html