In 1917, the Seattle Metropolitans, of the Pacific Coast Hockey Association (PCHA), became the first American-based team to win the Stanley Cup. They did so by defeating the Montreal Canadiens, of the National Hockey Association (NHA), 23 to 11 in a four-game, total-goal series. The games alternated between the seven-player rule of the PCHA and the six-player rule of the NHA.
The Seattle Metropolitans, 1917
Dolan, Edward F. The National Hockey League -- Toronto : Smithbooks, 1994. P. 29