The modern game originated in Canada in the 1800s, and the first modern indoor hockey game was played in Montreal in 1875. By the 1890s it had become extremely popular and had spread to the United States. Since 1917 the National Hockey League (NHL), with teams in both countries, has been the primary professional association. The rival World Hockey Association (WHA), launched in 1972, ceased operation in 1979; several of its 12 teams gained entry to the NHL. The NHL's current 30 teams play in two conferences, the Eastern and Western, each with two divisions. Though most NHL players have always been Canadian, an increasing number of players from the United States and Europe have appeared since the 1980s. Teams vie for the Stanley Cup—originally donated to the Canadian Amateur Hockey Association (1893) by Sir Frederick Arthur Stanley—the NHL's championship trophy and the symbol of world professional supremacy. In recent years the NHL has been marked by contentious labor relations, leading to a strike in 1992 and lockouts in 1994–95, 2004–5, and 2012–13; the 2004–5 lockout was so prolonged as to cancel the season.