Football, in its American version, is a physically tough team sport that rivals baseball as the most popular athletic event for spectators in the United States.  Millions watch football games on the interscholastic, intercollegiate, and professional levels.  Games are often accompanied by marching bands, halftime shows, and alumni or fan-club gatherings;  fierce loyalties develop on the part of some spectators.  On the intercollegiate and professional levels, crowds of 50,000 to 100,000 at games are common, and millions more watch football games on television. 
    Football is basically an autumn sport, with teams playing from 8 to 16 games, usually on successive weekends.  The best of the teams then enter postseason play-offs.  Many states have championships at the interscholastic (high school) level.  The best of the college teams play in several bowl games--the most popular being the Rose Bowl, the Sugar Bowl, the Orange Bowl, and the Cotton Bowl.  Although there is no one official college championship team, the unofficial intercollegiate champion is selected by a vote.  (Coaches, sportswriters, and broadcasters cast ballots.) The professional teams of the National Football League (NFL) culminate their season with the Super Bowl game, between the winners of the American and National conference play-offs. 
    Despite its tremendous popularity in the United States, football has remained basically an American sport.  Except for Canadians, who play the game with slightly altered rules (for example, 12 players to a side instead of 11 as in the U.S. game), the game has failed to take hold elsewhere.  This fact has added to the mystique of the sport's popularity in the United States. 
 
RULES OF AMERICAN FOOTBALL 
 

    The rules of football have evolved over a long time, partly because American football can be directly traced to rugby and the modifications that Americans made to that sport to develop their own version.  The rules are constantly changed to maintain a balance between offense and defense and to lessen the sport's violent nature.  A set of football rules is long and sometimes almost unwieldy;  high schools, colleges, and professionals play by three different sets of rules, which vary widely.  The rules are enforced by a number of officials on the field--ranging from four in high school games to seven in professional football. 
    A common denominator of all three levels of American football is the size of the field.  It is 100 yd (91.4 m) long with two additional 10-yd (9.14-m) areas called end zones.  The field is 53 1/3 yd (48.8 m) wide.  On the field, teams of 11 players line up in offensive and defensive positions.  Teams advance the ball by running with it, passing (throwing) it, and kicking it.  The lines at each end of the 100 yd are called goal lines, and the object of the game is for a player to cross the other team's goal line with the ball and thus score points. 
Scoring 
    When a player carries the ball over the opponent's goal line or passes the ball to a teammate, who either catches the ball in the end zone or catches it within the playing area and carries it over the goal line, the team is credited with a touchdown, worth six points.  A team can also score three points instead of trying for a touchdown by kicking the ball (a field goal) over the uprights above the crossbar (the goalpost) of the end zone that the opponent is defending.  The goalposts are stationed on the two end lines in all levels of football. Points can also be scored by stopping an opponent with the ball behind that opponent's own goal line (a safety, worth two points) and on a conversion play following a touchdown.  In a conversion attempt, the team that has scored the touchdown is given an opportunity to kick the ball through the uprights or advance it across the goal line again from the opponent's 2-yd line (the 3-yd line in college football).  In the National Football League, both types of conversion plays are worth one point;  in college play, kicking is worth one point, but advancing over the goal line by a run or a pass is worth two points. 
 

Operation of Play 
 

    College and professional games are 60 minutes long;  high school games are 48 minutes.  Play is divided into two halves, and the halves are divided equally so that in a complete game there are four quarters.  The games actually last much longer, however, because the clock is stopped after scores and for penalties, measurements, injuries, out-of-bounds plays, and incomplete passes.  Teams are allowed to take a limited number of time-outs;  they also leave the field to take a rest break at halftime, at which time they can readjust their strategies. 
    Play begins with a kickoff, in which a member of one team kicks the ball off the ground (from its own 35-yd line in NFL games; from the 40-yd line in college and high school play).  A coin flip just before the start of the game determines which team will perform the kickoff.  Subsequent plays are begun with the center hiking the ball (passing it backward through the legs or handing it underneath the legs to a quarterback stationed directly behind) from the point--called the scrimmage line--where the center's team has advanced the ball.  A play ends when the ballcarrier--a rusher (runner) or a pass-receiver--is tackled by an opponent;  falls to the ground (in professional football, he must be tackled to the ground); or runs out-of-bounds;  or when a forward pass is not completed (caught by a teammate). 
    The offensive team (the team in possession of the ball) lines up in different formations, dictated by strategy, and is allowed four plays, called downs, to advance the ball 10 yd. Each time the team does so, it is credited with a first down and is given four more downs to make 10 yd again.  If the team fails to advance 10 yd in any series of four plays, the opposition takes possession of the ball and goes on offense. Often a team that is stopped deep in its own territory with little chance of making the 10 yd will kick, or punt, the ball in order to put the opponent farther back in its own territory. At any point in the game, however, the defense can get the ball by intercepting a pass or recovering a fumble (dropped ball). Generally, football teams have specialists for both offense and defense, and the same players do not participate in both phases of the game, although they are allowed to. 
 

Equipment 
 

    The basic equipment for playing the game is a ball in the shape of an oblate spheroid 11-11 1/4 in (28-28.6 cm) long and 21 1/4-21 1/2 in (54-54.6 cm) around its longest axis;  the ball weighs 14-15 oz (396.9-425.25 g).  The goalposts vary in different levels of play.  In addition, players are heavily burdened with different types of protective equipment so that they resemble modern-day gladiators. 
 

HISTORY OF FOOTBALL 
 

    Any number of theories exist about the evolution of American football, but most historians agree that it is a modification of the English game of RUGBY and of soccer.  American football evolved slowly in the 19th century. 
19th-Century Development 
    Football made its first appearance at the intercollegiate level.  As a prelude to what would become an American game, collegians played rugby, but the sport was so grueling that it was barred at Harvard in 1860.  Nine years later, on Nov.  6, 1869, two New Jersey universities, Rutgers and Princeton, played what is considered the first intercollegiate game in the United States--although it hardly resembled modern-day football, or even the football that was played at the turn of the century.  There were 25 players on each side, and the scoring was decided by goals, not touchdowns, conversions, and field goals.  Rutgers won that first game, and Princeton won a rematch a week later.  Before long, other universities began taking up the game--Columbia in 1870, followed by Yale 2 years later. 
    Harvard continued to play a game more similar to rugby;  but in 1875, when it played Yale, Harvard convinced its opponent to play under new rules, which brought the game into a new era. Touchdowns counted only one point, compared to four for a successful conversion kick.  A field goal was worth five points. 
Walter CAMP, a freshman at Yale in 1876, became the organizational genius that the college game badly needed to unify and organize the rules.  Under his influence the teams were decreased in size from 15 to 11.  The field varied from 140 yd (128 m) by 70 yd (64 m) to 110 by 53 1/3 yd (100.5 by 48.8 m), and the ball was put in play by having the offensive team's center get the ball from his line of scrimmage to the quarterback.  In 1889, another innovation Camp shared in was the selection of the first All-America team, which started the trend toward glamorizing individual stars. 
The first significant rules convention was held in 1880.  The participants neglected, however, to provide incentives for advancing the line of scrimmage, thus sustaining the dull, 90-minute game.  In 1882, Camp successfully campaigned for the rule that made the offensive team give up possession if it moved the ball less than 5 yd forward in three downs. 
    Camp also standardized the scoring system in 1883, showing a strong prejudice toward the kicking influence of rugby and soccer.  Touchdowns scored only two points, whereas the conversion kick scored four and field goals five. 
20th-Century Innovations 
    Because of the violent, physical way in which football games were conducted in the 19th century, many deaths and maiming injuries occurred.  As a result of 18 deaths and 159 serious injuries in 1905, President Theodore Roosevelt insisted that the colleges make their game safer or he might ban it. Representatives of 62 colleges met in New York City after the 1905 season, and in early 1906 rules were suggested and approved that would eliminate the negative aspects.  The emphasis was shifted from brawn to speed and strategy.  The legalization of the forward pass made much of this possible. The game was also shortened from 70 to 60 minutes, and the required yardage for a first down was reset at 10 yd.  A neutral zone was set up between teams at the scrimmage line, and the offense had to have at least six men on the line of scrimmage, thus eliminating the dangerous plays in which blockers took running starts before the snap of the ball.  A seventh blocker on the line of scrimmage was mandated in 1910 to make the game even safer. 
    Football rules were changed constantly, however, to maintain the delicate offense-defense balance.  After 1912, however, when the number of chances to make a first down was increased to four, the changes were less drastic. 
 

The Passing Game 
 

    Modern football differs most from the turn-of-the-century game because of the skills of passers.  When the passing rule was instituted in 1906, few took advantage of it.  Actually, some rules limited its advancement, including the one that said that no pass could travel more than 20 yd beyond the line of scrimmage and the one that stated that an incomplete pass resulted in a 15-yd loss. 
    But the passing combination of quarterback Gus Dorais and Knute ROCKNE at Notre Dame in 1913 popularized the pass.  This aspect of the game brought fame to Notre Dame and its future coach Rockne, who became a legend.  Notre Dame defeated a powerful West Point team that year, with Dorais passing for 243 yd. 
    The ball was gradually made smaller over the years as passing became a more important part of the game.  Passing was instrumental in increasing interest in professional football, which lagged well behind college football until the 1950s.  The passing skills of such players as Sammy BAUGH, Otto GRAHAM, and Johnny UNITAS helped the professional sport achieve a rapid growth in popularity. 
Professional Football 
    The game was first played with paid players in 1895, when a team from Latrobe, Pa., hosted a game with a team from nearby Jeannette.  Except for barnstorming (touring) teams, however, there was little professional football of any significance until 1919, when the founders of what would become the National Football League met in Canton, Ohio, to organize the sport. Jim THORPE, the great American Indian star from Carlisle (Pa.) Indian School, was named president of the league in order to capitalize on his reputation as the most famous player up to that time. 
    Professional football grew slowly, however.  There were times of increased interest, such as the period during the 1920s when Red GRANGE of the University of Illinois signed to play professionally and drew crowds of 36,000 in Chicago and 68,000 in New York City.  The college teams, particularly those of such prestigious institutions as Notre Dame, Michigan, West Point, Southern California, Minnesota, Pittsburgh, and the Ivy League schools, still captured the attention of the sports public. 
    A second professional league, the All-America Football Conference, was founded in 1946 to compete with the NFL, but that league was absorbed by its competitor in 1950.  The coming of the television age and America's unending thirst for more sports after World War II helped the NFL grow.  By the late 1950s the televising of football games, which was held to a minimum by the colleges, was utilized by the professional teams to promote their game.  Rising attendance prompted the founding (1960) of a new circuit, the American Football League.  The NFL and AFL competed to sign new players and wisely loosened their rules to allow more scoring.  Before long they were competing on an equal level with the colleges for the football fan. 
    The AFL was absorbed by the NFL in 1970 as a result of a merger agreement in 1966.  From this agreement came a plan for a postseason championship game, which became known as the Super Bowl;  it was first played in January 1967.  It jumped to the top of the sports television ratings and has held that distinction ever since. 
    In 1974 another challenge to the NFL's professional "monopoly" appeared in the form of the World Football League.  Although the WFL lured several big-name stars away from the NFL, the new league was far less successful in the college draft and, more important, in attendance at their games.  The distinct inferiority of the WFL's drawing power and on-field talent, coupled with its lack of adequate financial backing, led to its demise after the 1975 season. 
The most recent challenge to the NFL is the new United States Football League, which began play in 1983, and whose season runs from late winter to late spring--with no overlap with the NFL schedule.  The 14 teams of the USFL, in 2 conferences, have been relatively successful in signing their draftees to contracts (including the Heisman Trophy winners Herschel WALKER and Doug FLUTIE), and have contracts with both network and cable television stations to broadcast their games.  Because of lagging attendance, however, the league changed to a fall schedule in 1986. 
    In the meantime, the NFL suffered a 1982 mid-season player strike that substantially reduced the length of the season and alienated many football fans.  The players' association did not achieve many of their goals, and most experts viewed the results (no free agency for another 5 years, for example) as beneficial in the long run for only about one-third of the NFL players. 

Canadian Football 
 

    Like U.S. football, Canadian football developed from rugby and soccer during the late 19th century.  In 1909, Lord Grey, governor-general of Canada, donated a trophy--subsequently called the Grey Cup--to be awarded annually to Canada's best football team.  Although Grey Cup play became predominantly professional during the 1930s, amateur teams were not banned until 1956, when the current structure of the organization that would become (1960) the Canadian Football League (CFL) was solidified.  Canadian football is similar to its U.S. professional counterpart but differs in the following significant ways:  the field is 110 yd (100.6 m) long and 65 yd (59.4 m) wide, with 25-yd-deep (22.9-m) end zones;  there are 12 players per team on the field;  the offensive team has 3 downs to gain 10 yd;  an untouched punt or unsuccessful field-goal attempt may be recovered by the kicking team;  after scoring a touchdown, a team may try for 2 points;  a team can score a rouge--worth 1 point--if their opponents fail to run a kick out of their own end zone. 
 

Picture Captions 
 

    The contact involved in football requires that players wear padding to protect ribs, hips, and upper torso.  The basic gear includes: the ball, an inflated, leather-sheathed rubber bladder; a helmet with a protective face guard; and shoes equipped with cleated soles for traction. 

Jim Brown (1936-  ), for a time the leading rusher in the history of professional football, smashes through the Philadelphia Eagles' defense. After setting numerous records during his nine seasons with the Cleveland Browns, he retired in 1965 to pursue an acting career. 

Joe Namath (1943-  ), who quarterbacked the University of Alabama to three bowl appearances and a national championship, ushered in the era of the high-paid star athlete when he signed a $427,000 contract with the New York Jets of the American Football League in 1965.  Namath's greatest success occurred in the 1969 Super Bowl, when he led the Jets to a 16-7 upset victory over the National Football League's Baltimore Colts. 

Doug Flutie (1962-  ) won the 50th Heisman Trophy as collegiate player of the year in 1984.  In four years (1981-85) at Boston College, Flutie became the first collegiate quarterback to pass for more than 10,000 yards. 

Joe Montana (1956-  ) was the National Football League's premier quarterback during the 1980s. Montana's career rating is the highest in NFL history, as is his percentage of passes completed--about 64%. He holds many regular-season and Super Bowl records. 

Running back Walter Payton (1954-  ) became the NFL's all-time leading rusher in 1984, surpassing the legendary Jim Brown. 

After joining the Dallas Cowboys, Roger Staubach (1942-  ) led the NFL in passing in 1973, 1978, and 1979, and prior to his retirement in 1980 had piloted the Cowboys to 7 divisional, 5 league, and 2 Super Bowl championships. 

Quarterback Fran Tarkenton (1940-  ) holds virtually all of the career passing records in the National Football League, and he gained more yards on the ground than any quarterback in NFL history.  Upon his retirement in 1977, he became a sports commentator. 

Johnny Unitas (1933-  ) joined the Baltimore Colts in 1956 and, in 17 seasons as their quarterback, led them to 4 NFL championships. Unitas was the NFL's Player of the Year in 1959, 1964, and 1967, and he made 10 All Star game appearances. 

Vince Lombardi (1913- ), himself an outstanding football player at Fordham University, compiled an enviable record of success as a coach of high school, collegiate, and professional football teams.  During a nine-year span, Lombardi guided the Green Bay Packers to five NFL championships through his authoritarian coaching methods, developed to motivate athletes to perform to the height of their abilities. 

Norwegian-born Knute Rockne's tenure as football coach for the University of Notre Dame (1918-31) included 5 undefeated seasons. Rockne was an early promoter of the forward pass. 

One of the greatest athletes who ever lived, Jim Thorpe (1888-1953) excelled in baseball, football, and track.  In the 1912 Olympic Games, Thorpe won the decathlon and pentathlon; in football, he once scored 25 touchdowns and 198 points in a single season. 

The short-lived United States Football League (1983-86) was built around running back Herschel Walker (1962- ); when it failed he signed a five-year, $5 million contract with the NFL's Dallas Cowboys. Walker, at 6 ft l l/2 in (1.87 m), 220 lb (100 kg), is known for his strength and power as well as his speed.