Football is one of the most popular sports in America, so popular that the National Football League (NFL) has the highest average attendance of any sports league in the world. The championship game, the Super Bowl, is one of the most watched events on television each year. The American version of the game is often referred to as 'American football' in order to distinguish it from soccer, which is called football in other parts of the world.

Origins of the Game
American football has its origins in various forms of rugby and soccer played in Britain in the mid–19th Century, in which a ball is kicked at a goal or run over a line. The roots of these games can in turn be traced to traditional ball games played at villages and schools in Europe many centuries before. When European settlers came to America, they brought the games with them.

The birth date of football in the United States is generally regarded by historians as November 6, 1869, when teams from Rutgers and Princeton Universities met for the first intercollegiate football game. In those early games, there were 20 players to a team and football still more closely resembled rugby than football as we know it today. After Princeton and Rutgers got things started, other Eastern universities began to play the game. Next was Columbia University, and later Harvard and Yale. In 1873, representatives from Columbia, Princeton, Rutgers and Yale met to formalize rules. However, these rules were based mostly on soccer.

Rules Conventions and Walter Camp
In 1880 the sport really began to take shape due largely to the influence of one person: Walter Camp. Camp was a student at Yale from 1876 to 1882, where he was an avid athlete and played on the football team. He was a fixture at the rules conventions. It was in 1880 that the rules committee began to adopt his ideas. These included establishing the line of scrimmage, the exchange between a quarterback and a center, awarding six points for a touchdown and three points for a field goal (though it would take years to come to those exact numbers), lowering the number of players to 11 per side, setting the length of the playing field at 100 yards, and the concept of set plays. Camp was also responsible for introducing the system of downs. After first allowing three attempts to advance the ball five yards, in 1906 the distance was changed to ten yards. The fourth down was added in 1912. After Camp left Yale as a student, he continued to coach the team and was a regular presence at every rules convention held until his death in 1925.
Safety Threatens the Game
Within a decade, concern over the increasing brutality of football led to its ban by some colleges. Nearly 180 players had suffered serious injuries, and eighteen deaths had been reported from the brutal mass plays that had become common practice. In 1905, President Theodore Roosevelt called upon Harvard, Princeton, and Yale to help save the sport.

At a meeting between the schools, reform was agreed upon, and at a second meeting, attended by more than sixty other schools, the group appointed a seven member Rules Committee and set up what would later become known as the National Collegiate Athletic Association, or the NCAA.

From this committee came the legalization of the forward pass, which resulted in a redesign of the ball and a more open style of play on the field. The rough mass plays, which once caused so many serious injuries, were prohibited by the committee. Also prohibited was the locking of arms by teammates in an effort to clear the way for their ball carriers. The length of the game was shortened, from seventy to sixty minutes, and the neutral zone was established. The neutral zone separates the teams by the length of the ball before each play begins.

The Birth of Professional Football
Outside of colleges, the game of football was played by athletic clubs. By the 1880s, most athletic clubs in America had a team playing football. The players on these teams were not paid. However as competition mounted, money entered the game.

The first evidence of someone being paid to play a football game came on November 12, 1892. The Allegheny Athletic Association (AAA) played the Pittsburgh Athletic Club in Pittsburgh, and William “Pudge” Heffelfinger was paid $500 by the AAA. One year later the Pittsburgh Athletic Club signed one of their players, halfback Grant Dibert, to the first professional football contract. That same year, three other players signed contracts with the Allegheny Athletic Association.

On August 20, 1920, a meeting was held by representatives of the Akron Pros, Canton Bulldogs, Cleveland Indians, and Dayton Triangles at an auto showroom in Canton, Ohio. This meeting resulted in the formation of the American Professional Football Conference (APFC). The goal of the organizers was to raise the standards of the game and work together on the formation of schedules. The league, which consisted of fourteen teams, hired Jim Thorpe as its first president. In 1922 the league changed its name to the National Football League (NFL).

Up until the 1960's, the NFL was the dominant professional football league and faced little competition. That changed when the American Football League (AFL) began play that year. The AFL gained in popularity, winning lucrative television contracts and engaging in bidding wars with the NFL for free agents and draft picks.

The two leagues announced a merger on June 8, 1966, to take full effect in 1970. In the meantime, the leagues held a common draft and championship game. The game, the Super Bowl, was held four times before the merger, with the NFL winning Super Bowl I and Super Bowl II, and the AFL winning Super Bowl III and Super Bowl IV. After the leagues merged, it was reorganized into two conferences: the National Football Conference (NFC) and the American Football Conference (AFC).

Basics of the Game
While the rules of football are constantly changing, the basics of the game remain the same. The object is to score more points than your opponent in the allotted time, which is broken into four segments called 'quarters'. Prior to the start of the game a coin is tossed. The team who wins the coin toss gets to choose if it will kick or receive first and from which side of the field it will start.

The game begins with a 'kick-off' where the defense team punts the ball down field to the offense who then runs back with the ball as far as possible toward the defensive team's 'end zone' before being tackled. To score points teams move the ball down the field attempting to get it into the opposing team's 'end zone' for a touchdown. This can be achieved by either throwing the ball to a teammate or running with the ball into the end zone.

The offensive team gets 4 chances, called 'downs', to move the ball 10 yards forward. Once the offensive team reaches 10 yards the downs are reset, and the team tries again for another 10 yards. If after 4 downs the team has not gained 10 yards, the ball is turned over to the defensive team who now becomes the offense. Sides will also switch if a player on the offense throws a forward pass and the defense intercepts it, or when an offensive player drops the ball or has it knocked out of his hands and the defensive team jumps on it.

When a player scores a touchdown six points are awarded to his team. A touchdown can be scored by either carrying the ball into the end zone or receiving the ball from a pass while in the end zone. After a touchdown has been scored the offensive team has the opportunity to kick the ball for an extra point. The ball must pass between the upright posts for a successful kick.

A 'field goal' can be scored from anywhere on the field at any time (usually on the final down) and a successful kick will result in three points. A 'safety' is scored when the defensive team manages to tackle an opponent into the defense's own end zone. For this the offensive team receives 2 points. The team with the most points at the end of the game wins. In the event of a tie, there is a complex method for breaking it. The methods vary depending on the level of play - professional, college or high school.