The North American Masters Tournament is a tournament for professional Go players in the United States, Canada and Mexico. Unusually for a professional tournament, most of it is played over the Internet (on IGS). The final best-of-3 match is, however, usually played over the board at the U.S. Go Congress.
So far the event has been won every year by Jiang Zhujiu:
Further details and full results for every year can be found at http://www.usgo.org/NAMT/ .