Thanksgiving is ruled by two very powerful f-words: "food" and "football." Nearly as old as the sport itself, the tradition of watching football on Thanksgiving began in 1876, when the newly formed American Intercollegiate Football Association held its first championship game. Less than a decade later, more than 5,000 club, college and high school football teams held games on Thanksgiving, with match-ups between Princeton and Yale drawing more than 40,000 fans out from their dining rooms. 1934 marked the first NFL game held on Thanksgiving when the Detroit Lions took on the Chicago Bears. The Lions have played on Thanksgiving ever since except, of course, when the team was called away to serve during World War II.