Rivalries in the National Hockey League have occurred between many teams and cities. Rivalries have arisen among NHL teams for many different reasons, the primary ones including geographic proximity, familiarity with opponents, on-ice incidents, and cultural, linguistic, or national pride. The importance of these various factors has varied widely throughout the history of the league. Early history During the earliest days of the NHL, the league was limited strictly to Central Canada, and all cities in the league were in close proximity, making for bitter rivalries all around. In addition, Montreal had two teams representing its English-French divide. The "French" Canadiens battled the "English" Wanderers (and later the Maroons). Rivalries also existed with other leagues, such as the Pacific Coast Hockey Association. It was not until 1926 that the NHL took sole ownership of the Stanley Cup. By that time, the league began expanding into the United States, and new rivalries were created. Rapid expansion into the U.S. for a short time created a cross-town rivalry in New York City between the New York Rangers and New York Americans. The economic turmoil of the Great Depression and World War II, however, forced several teams to fold, with the result that by 1942 the NHL consisted of only 6 teams. Original Six rivalries From –, only six teams (the Boston Bruins, Chicago Blackhawks, Montreal Canadiens, Detroit Red Wings, New York Rangers, and Toronto Maple Leafs) played in the NHL. With only 6 opponents, teams played more frequently and games were often underscored by personal rivalries between players. These personal and team rivalries lasted for many years, as the turnover rate on NHL rosters was very low. At one point or another, during this era, all the teams had animosity towards one another. Eastern Conference Atlantic Division The Atlantic Division was formed in 1974 as the Adams Division, which beginning in 1981 had all its teams in Eastern Canada and New England with the exception of the Buffalo Sabres, which are located in Western New York. The division became the Northeast Division in 1993, and then the Atlantic Division in 2013. Battle of Ontario: Ottawa Senators vs. Toronto Maple Leafs The Battle of Ontario is a rivalry between the Ottawa Senators and Toronto Maple Leafs. The teams compete in the same division and meet frequently during regular season games. In the early 2000s, the teams met four times in the playoffs with