Early history[ edit ] American football evolved from the sports of association football soccer and rugby football. Rugby football, like American football, is a sport where two competing teams vie for control of a ball, which can be kicked through a set of goalposts or run into the opponent's goal area to score points.
The game was played between two teams of 25 players each and used a round ball that could not be picked up or carried. It could, however, be kicked or batted with the feet, hands, head or sides, with the ultimate goal being to advance it into the opponent's goal.
Rutgers won the game 6 goals to 4. Representatives of Yale, Columbia , Princeton and Rutgers met on October 19, to create a standard set of rules for all schools to adhere to. Harvard abstained from the conference, as they favored a rugby-style game that allowed running with the ball.
These players introduced the sport to Princeton, a feat the Professional Football Researchers Association compared to "selling refrigerators to Eskimos. Yale player Walter Camp , now regarded as the "Father of American Football",   secured rule changes in that reduced the size of each team from 15 to 11 players and instituted the snap to replace the chaotic and inconsistent scrum.
Prior to the snap, the strategy had been to punt if a scrum resulted in bad field position. However, a group of Princeton players realized that, as the snap was uncontested, they now could hold the ball indefinitely to prevent their opponent from scoring.
In , both teams in a game between Yale-Princeton used this strategy to maintain their undefeated records. Each team held the ball, gaining no ground, for an entire half, resulting in a 0—0 tie. This "block game" proved extremely unpopular with the spectators and fans of both teams. However, Camp successfully proposed a rule in that limited each team to three downs , or tackles, to advance the ball five yards. Failure to advance the ball the required distance within those three downs would result in control of the ball being forfeited to the other team.
This change effectively made American football a separate sport from rugby, and the resulting five-yard lines added to the field to measure distances made it resemble a gridiron in appearance. Other major rule changes included a reduction of the field size to by Morris highlighting the dangers that were associated with the sport Despite these new rules, football remained a violent sport.
Dangerous mass-formations, which involved interlocking interference, like the flying wedge resulted in serious injuries and deaths. Other rule changes introduced that year included the reduction of the time of play from 70 to 60 minutes and the increase of the distance required for a first down from 5 to 10 yards 9. To reduce infighting and dirty play between teams, the neutral zone was created along the width of the football.
This is the first recorded instance of a player being paid to participate in a game of American football , although many athletic clubs in the s offered indirect benefits, such as helping players attain employment, giving out trophies or watches that players could pawn for money, or paying double in expense money. Despite these extra benefits, the game had a strict sense of amateurism at the time, and direct payment to players was frowned upon, if not outright prohibited.
The National Football League NFL , a group of professional teams that was originally established in as the American Professional Football Association, aimed to solve these problems. This new league's stated goals included an end to bidding wars over players, prevention of the use of college players, and abolition of the practice of paying players to leave another team.
The game, a 23—17 overtime victory by the Colts, was seen by millions of television viewers and had a major impact on the popularity of the sport. This, along with the innovations introduced by the new American Football League AFL in the early s, helped football to become the most popular sport in the United States by the mids.
The bidding war for players ended in , when NFL owners approached the AFL regarding a merger, and the two leagues agreed on one that would take full effect in This agreement provided for a common draft that would take place each year, and it instituted an annual World Championship game to be played between the champions of each league.
That game began play at the end of the season. Once the merger was completed, it was no longer a championship game between two leagues, and reverted to the NFL championship game, which came to be known as the Super Bowl. Each bowl game would be associated with a particular conference, and earning a spot in a bowl game was the reward for winning a conference.
This arrangement was profitable, but it tended to prevent the two top-ranked teams from meeting in a true national championship game, as they would normally be committed to the bowl games of their respective conferences.
Several systems have been used since to determine a national champion of college football. The first was the Bowl Coalition , in place from to American football positions A football game is played between two teams of 11 players each. NFL teams are required to number their players by a league-approved numbering system, and any exceptions must be approved by the Commissioner. The offense red is lined up in a variation of the I formation , while the defense blue is lined up in the 4—3 defense.
Both formations are legal The offensive team must line up in a legal formation before they can snap the ball. An offensive formation is considered illegal if there are more than four players in the backfield or fewer than five players numbered 50—79 on the offensive line. Interior offensive linemen are not allowed to move until the snap of the ball. The quarterback is the leader of the offense.
Either the quarterback or a coach calls the plays. Quarterbacks typically inform the rest of the offense of the play in the huddle before the team lines up. The quarterback lines up behind the center to take the snap and then hands the ball off, throws it or runs with it. Halfbacks may also serve as receivers. Fullbacks tend to be larger than halfbacks and function primarily as blockers, but they are sometimes used as runners in short-yardage situations  and are seldom used in passing situations.
The principal receivers are the wide receivers WR and the tight ends TE. The main goal of the wide receiver is to catch passes thrown by the quarterback,  but they may also function as decoys or as blockers during running plays. Tight ends line up outside the tackles and function both as receivers and as blockers. Defensive ends line up on the ends of the line, while defensive tackles line up inside, between the defensive ends.
The primary responsibilities of defensive ends and defensive tackles is to stop running plays on the outside and inside, respectively, to pressure the quarterback on passing plays, and to occupy the line so that the linebackers can break through. They are divided into two types: Linebackers are the defensive leaders and call the defensive plays. Their diverse roles include defending the run, pressuring the quarterback, and guarding backs, wide receivers and tight ends in the passing game.
Safeties are themselves divided into free safeties FS and strong safeties SS. Safeties are the last line of defense, and are responsible for stopping deep passing plays as well as running plays. The special teams unit of the team in control of the ball will try and execute field goal FG attempts, punts and kickoffs , while the opposing team's unit will aim to block or return them. The long snapper's job is to snap the football to the holder, who will catch and position it for the placekicker.
There is not usually a holder on kickoffs, because the ball is kicked off of a tee; however, a holder may be used in certain situations, such as if wind is preventing the ball from remaining upright on the tee. The player on the receiving team who catches the ball is known as the kickoff returner KR. The long snapper snaps the football directly to the punter, who then drops and kicks it before it hits the ground.
Gunners line up split outside the line and race down the field, aiming to tackle the punt returner PR — the player that catches the punt. Upbacks line up a short distance behind the line of scrimmage, providing additional protection to the punter.