American football

American football is a sport played between two teams of eleven with the objective of scoring points by advancing the ball into the opposing team's end zone. It is known in the United States simply as football, and it may be referred to as gridiron informally or outside the United States and Canada.^[1][2] The ball can be advanced by running with it or throwing it to a teammate. Points can be scored by carrying the ball over the opponent's goal line, catching a pass thrown over that goal line, kicking the ball through the opponent's goal posts or tackling an opposing ball carrier in his own end zone.

In the United States, the major forms are high school football, college football and professional football, which are played under slightly different rules.^[3] High school football is governed by the National Federation of State High School Associations, while college football by the National Collegiate Athletic Association and National Association of Intercollegiate Athletics. The major league for professional football is the National Football League (NFL). Other minor professional leagues also exist in the U.S., and may also have slightly different rules from those of the NFL.

The sport is also played in Europe,^[4][5][6] Japan, Mexico, and other several countries. The International Federation of American Football acts as an international governing body for the sport, but the organization has little standing in the United States.

American football is closely related to Canadian football but with some differences in rules and the field.^[7] Both sports can be traced to early versions of association football and rugby football.

History

The history of American football can be traced to early versions of rugby football and association football. Both games have their origins in varieties of footballplayed in the United Kingdom in the mid-19th century, in which a ball is kicked at a goal and/or run over a line. Many games known as "football" were being played at colleges and universities in the United States in the first half of the 19th century.

American football resulted from several major divergences from rugby football, most notably the rule changes instituted byWalter Camp, considered the "Father of American Football". Among these important changes were the introduction of theline of scrimmage and of down-and-distance rules. In the late 19th and early 20th centuries, game play developments by college coaches such as Eddie Cochems, Amos Alonzo Stagg, Knute Rockne, and Glenn "Pop" Warner helped take advantage of the newly introduced forward pass.

The popularity of collegiate football grew as it became the dominant version of the sport for the first half of the twentieth century. Bowl games, a college football tradition, attracted a national audience for collegiate teams. Bolstered by fiercerivalries, college football still holds widespread appeal in the US.

The origin of professional football can be traced back to 1892, with William "Pudge" Heffelfinger's $500 contract to play in a game for the Allegheny Athletic Association against the Pittsburgh Athletic Club. The first Professional "league" was theOhio League, formed in 1903, and the first Professional Football championship game was between the Buffalo Prospects and the Canton Bulldogs in 1919. In 1920, the American Professional Football Association was formed. The first game was played in Dayton, Ohio on October 3, 1920 with the host Triangles defeating theColumbus Panhandles 14–0. The league changed its name to the National Football League (NFL) two years later, and eventually became the major league of American football. Initially a sport of Midwestern industrial towns in the United States, professional football eventually became a national phenomenon. Football's increasing popularity is usually traced to the 1958 NFL Championship Game, a contest that has been dubbed the "Greatest Game Ever Played". A rival league to the NFL, the American Football League (AFL), began play in 1960; the pressure it put on the senior league led to a merger between the two leagues and the creation of the Super Bowl, which has become the most watched television event in the United States on an annual basis.

Field and players

American football is played on a field 360 by 160 feet (120.0 by 53.3 yards; 109.7 by 48.8 meters).^[13] The longer boundary lines are sidelines, while the shorter boundary lines are end lines. Sidelines and end lines are out of bounds. Near each end of the field is a goal line; they are 100 yards (91.4 m) apart. A scoring area called an end zone extends 10 yards (9.1 m) beyond each goal line to each end line. The end zone includes the goal line but not the end line.^[13] While the playing field is effectively flat, it is common for a field to be built with a slight crown—with the middle of the field higher than the sides—to allow water to drain from the field.

Yard lines cross the field every 5 yards (4.6 m), and are numbered every 10 yards from each goal line to the 50-yard line, or midfield (similar to a typicalrugby league field). Two rows of short lines, known as inbounds lines or hash marks, run at 1-yard (91.4 cm) intervals perpendicular to the sidelines near the middle of the field. All plays start with the ball on or between the hash marks. Because of the arrangement of the lines, the field is occasionally referred to as a gridiron in a reference to the cooking grill with a similar pattern of lines.

At the back of each end zone are two goalposts (also called uprights) connected by a crossbar 10 feet (3.05 m) from the ground. For high skill levels, the posts are 18 feet 6 inches (5.64 m) apart. For lower skill levels, these are widened to 23 feet 4 inches (7.11 m).

Each team has 11 players on the field at a time. Usually there are many more players off the field (an NFL team has a limit of 53 players on their roster, all of which can be dressed for a game). However, teams may substitute for any or all of their players during the breaks between plays. As a result, players have very specialized roles and are divided into three separate units: the offense, thedefense and the special teams. It is rare for all team members to participate in a given game, as some roles have little utility beyond that of an injury substitute.