History
USA Water Polo has usually held two national championships, in summer and winter. The summer tournament was traditionally played outdoors, the summer tournament indoors, using a somewhat smaller pool.
Before World War II, the summer tournament was generally considered the true national championship. Since then, though, the outdoor tournament has been the more prestigious of the two.
Since 2001, the winter tournament has been called the Open Championship and the summer tournament has been called the National Championship.