Football, in the United States and Canada, team sport in which the object is to deliver a ball over a goal line and to prevent the opposing team from reaching its own goal line at the opposite end of a demarcated field. Teams include 11 men. The field is 100 yd (91.4 m) long by 53 1/3 yd (48.7 m) wide. Lines are marked across the field at 5-yd (4.6-m) intervals. Behind each goal line is an area 10 yd (9.1 m) deep called the end zone, at the end of which is the goal post. A touchdown—running or passing the ball (to a receiver) over the goal line—is worth 6 points. The field goal, or place-kick over the crossbar and between the goalpost uprights, is worth 3 points. A safety, where a man in posession of the ball is downed in back of his own goal line, is 2 points. A conversion kick, allowed after each touchdown, is worth 1 point; an alternative in college play is the 2-point conversion, which allows the ball to be run or passed over the goal line. Officials may penalize a team by moving the ball closer to its goal line when it violates a rule. Minor fouls cost 5 yd (4.6 m). Major fouls are penalized 15 yd (13.7 m).
Early games, dating back to about 1820 in the eastern United States, were informal, soccerlike affairs. In 1880, along with a new method of putting the ball into play (by the holder snapping it back with his foot to the quarterback), came the “block game.” Teams took the kickoff and retained the ball with no effort to advance it, resulting in dull, scoreless ties. Yale University coach Walter Camp solved this problem by the system of downs that became a rule in 1882. The team in possession was given 3 plays, or downs, to advance the ball 5 yd (4.6 m). If successful, it retained possession and started another series of 3 downs; it if failed it had to turn the ball over to the opponent. This rule—changed to 10 yd (9.1 m) in 4 downs in 1912—has remained the heart of American football. It led to the use of strategy, to the disuse of kicking as the predominant offense, and to the development of the running attack by short, hard rushes. A rule in 1894 decreed that the ball had to travel at least 10 yd (9.1 m) on the kickoff. This put a stop to the dangerous “V trick” and later flying wedge, whereby the “kicker” merely touched his toe to the ball, picked it up, tucked himself within a wedge formed by his teammates, and ran to a huge gain against his foes. Nevertheless, with players left largely unprotected by primitive helmets and pads, the concentrated power plays were causing many injuries, even deaths. President Theodore Roosevelt, himself a fan, demanded that football be made safer, and in 1906 mass formations, hurdling, and other dangerous strategems were banned. The game was reduced from 70 to 60 min, and the forward pass was legalized. In college football, the new open game spawned the breakaway halfbacks, players with speed and agility in carrying the ball, like Jim Thorpe of the Carlisle Indian School and, in the early 1920s, Harold “Red” Grange of the University of Illinois.
Free substitution was permitted in 1941, but the rule was not exploited until 1945, when Fritz Crisler of Michigan divided his team into offense and defense platoons. Soon all teams were using the 2-platoon system, costs soared, and in 1953 free substitution was outlawed by the Football Rules Committee. It was restored during the early 1960s, largely to compete with the flourishing pro leagues, which had adopted it. Ex-collegians who worked in the small industrial towns of western Pennsylvania and formed pickup teams during the 1890s were the first professionals; they received $10 a game, when paid. In 1920 at Canton, Ohio, 11 teams formed the United States Professional Football Association, with Jim Thorpe as its president and star player. Franchises, today worth millions, cost $100 each.
The league changed its name to the National Football League (NFL) in 1921 but did not begin to gain recognition until the signing in 1925 of Illinois star Red Grange; other college stars followed as the league prospered. In 1933 the league reorganized into 10 teams, mostly in major cities and evenly divided between 2 divisions. The annual college draft was initiated in 1935, giving weaker clubs the first chance to select college stars and thus maintaining a talent balance. By 1946 interest in pro football had grown to a point where a second league, the All America Conference (AAC), was started. It lasted only 4 seasons. During the 1960s attendance records climbed due to the wide-open style of play and the spectacle of violence created by agile, 260–lb linemen crunching into each other and sometimes into the game's lighter specialists. In 1960 the American Football League (AFL) started play. Green Bay, coached by Vince Lombardi, beat the AFL's Kansas City team in 1967 in the first Super Bowl, which pitted the NFL champion against the AFL champion. In 1970 the NFL's 16 teams combined with the AFL's 10 to form the National Football League, which is divided into National and American conferences (with 3 divisions within each conference) that correspond roughly to the old NFL-AFL alignments. The Canadian Football League has a total of 8 teams in its 2 divisions.