In the United States, indoor football is football played at ice hockey-sized indoor arenas (as opposed to certain NFL teams which have large indoor stadiums, such as the New Orleans Saints who play in the Mercedes-Benz Superdome). While varied, the rules of indoor football are designed to allow for play in a smaller arena. The indoor football season typically begins in mid- to late-winter and ends by mid-summer.
The first documented indoor football games were those played at the Chicago Coliseum in the late 1890s. The first such game matched Michigan against Chicago on Thanksgiving Day 1896. The match was "the first collegiate game of football played under a roof."   Adding to the novelty, as daylight turned to darkness, the field inside the Coliseum was lit with electric lighting.  With seven acres of floor space, the sprawling Coliseum is believed to have not needed any compromises to accommodate an American football field. According to a newspaper account, the field grew dark in the second half, and play was halted for ten minutes to discuss whether play should continue. Play was resumed, and the lights were finally turned on after Michigan scored a touchdown.  The press proclaimed the experiment in indoor football to be a success:
One thing at least was settled by the game, and that is, that indoor football is literally and figuratively speaking a howling success. The men had no trouble in catching punts, and football was played on its merits, without the handicaps of a wet field or a strong wind. Toward the end of the second half it got very dark, and the spectators were treated to a novelty in the shape of football by electric light." 
Although both critically and commercially successful, the Coliseum was destroyed in a fire less than two years after its opening, and its replacement could not accommodate an American football field.
Later, at Madison Square Garden in 1902 and 1903, there were games known as the " World Series of Pro Football." The games were played on a 70-yard by 35-yard dirt field but otherwise adhered to outdoor rules. Poor attendance led to the tournament being discontinued after two years. 
The Chicago Bears of the National Football League hosted an experimental game against their crosstown rivals, the Cardinals, after the 1930 NFL season, at the indoor Chicago Stadium.  Two years later, poor weather conditions led to the Bears hosting the 1932 NFL Playoff Game against the Portsmouth Spartans (now the Detroit Lions) at the stadium.       A dirt and tanbark field measuring 80 yards long (60 yards plus two ten-yard end zones) and 45 yards wide was constructed on the arena's floor. The Chicago Stadium games were notable for introducing several rule changes: hash marks were introduced to keep play away from the spectators, who were seated right next to the field (much like modern indoor football), teams were penalized 20 yards upon crossing midfield, and goal posts were moved up to the goal line. (The Bears' official Web site goes further and claims that field goals were outlawed for the 1932 game.) 
In 1930, the Atlantic City Convention Center constructed a full-size indoor football field, and used it for one to three games a year during the 1930s; the stadium stopped hosting games in 1940 and did not resume hosting football games until 1961. In the 1960s the Boardwalk Bowl, a post-season game involving small college teams, was contested at the convention center. The Bowl was an attempt to make Atlantic City more of a year-round resort in the pre-gambling era as opposed to a single-season one (the Miss America Pageant, also held at the center, likewise began as an attempt to extend the season beyond Labor Day). The Atlantic Coast Football League played its inaugural championship game at the convention center in 1962, but the game only drew 2,000 fans and the game would thereafter move to the home stadium of the team with the best regular season record. The Philadelphia-based Liberty Bowl game, which had been played at Municipal Stadium from 1959–1963, was moved into the Convention Center in 1964 for the contest between Utah and West Virginia. The game drew just over 6,000 fans, though, and the Liberty Bowl moved to Memphis the next year, where it is still held as of 2017.
Unlike modern indoor football, the size of the playing surface and hence the rules were essentially the same as in the standard outdoor game, with rules updated to deal with contingencies for what could happen indoors, such as a punt striking the ceiling. The end zones were slightly shorter—eight yards instead of the standard ten.
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While several attempts to create a true indoor football game have been made since shortly after American football was developed, the first version to meet with relatively widespread success and acceptance is Arena football, devised by Jim Foster, a former executive of the United States Football League and the National Football League. He devised his game while watching indoor soccer,[ citation needed] another game derived from a sport played outdoors. He worked on the game in the early 1980s, but put any plans for full development of it on hold while the United States Football League, an attempt to play traditional American football in a non-traditional (spring-summer) season, was in operation in 1983–1985. When the USFL ceased operations, Foster saw his opportunity. He staged a "test" game in Rockford, Illinois in 1986 and put together a four-team league for a "demonstration season" in the spring of 1987, with games televised on ESPN.
Foster had to adopt a field that would fit within the smaller playing surfaces found in most arenas and thus created a field that was identical in size to a standard professional ice hockey rink, 200 by 85 feet (61 m × 26 m). This resulted in the field being 50 yards long (half of the length of a standard American football field) with eight-yard end zones (which may, if necessary, be curved in the end zones as hockey rinks are), and the field being slightly over half as wide as a standard football field. Although it was not as much of an issue then as it is now, Foster adopted artificial turf (such as AstroTurf) for the field, because of its ability to be rolled up when the arena is being used for other sports.
Foster adopted a modified version of eight-man football. He also mandated a one-platoon system that required at least six players "go both ways", playing on both offensive and defensive downs. This had the added desirable effect of limiting team payrolls.
There were numerous other rules designed to help the offense and ensure high-scoring games:
- the banning of punting, meaning that if a team felt it was not likely to get a first down after three plays its only kicking option was to attempt a field goal.
- the placing of rebound nets around the ends of the playing surface; kicked and passed balls bounced off these nets and remained in play. In the case of a pass, the ball is live only until it touches the ground, but in the case of an unsuccessful field goal or a kickoff, the ball remains in play unless it goes out of bounds or until the player recovering it is downed by contact or scores. This means that on every kicking play except an extra point attempt, either team may have a shot to regain the ball and advance it, much as a blocked kick could be in the traditional outdoor game. Only kicked or passed balls touching the slack nets behind the goalposts are ruled dead at that point.
To further an offensive passing advantage over the defense, Foster also imposed strict restrictions on the defensive formation, mandating that all defenses played a 3-2-Monster formation (three defensive linemen, two linebackers, two cornerbacks, and one safety). Linebackers were not permitted to blitz and were required to stay in boxes behind the line of scrimmage, while defensive linemen where hindered by restrictions that prevented them from using certain techniques to penetrate the offensive line. Quarterbacks and placekickers were exempt from the one-platoon system, allowing two key scoring positions to be more specialized. The AFL also adopted the USFL's concept of playing in the late spring and summer, since this is when most hockey and basketball arenas have the fewest schedule conflicts (only competing with touring stadium rock concerts). The spring schedule has since been imitated by virtually all other professional indoor leagues as of 2010.
Within a year of the AFL kicking off, its first challenger, the World Indoor Football League formed. The WIFL planned to play a schedule with six teams beginning in summer of 1988 with its own set of indoor-inspired rules, including an unusual system that would have eight men on offense and seven men on defense. Despite having backing from former NFL players, veteran coaches, and singer John Mellencamp, the league canceled its 1988 season, folded half of its franchises (including Mellencamp's), and made an unsuccessful bid for the remaining three teams to join the AFL.
In 1990, Foster patented the rules of Arena football, meaning that only persons authorized by him could use his rules and his name for the sport. While the AFL asserted throughout the 1990s that the patent covered virtually every aspect of the game (from the 50-yard field to the eight-man format), a 1998 lawsuit (Arena Football League v. Professional Indoor Football League) established that the patent specifically covered the rebound net feature, meaning that competitors and imitators who attempted to copy the game couldn't use this aspect of the rules.  However, under provisions of U.S. patent law, Foster's patent expired on March 27, 2007, enabling imitators to use his rebound nets (at least as originally envisioned, without other innovations that he may have patented).
The most remarkable development in Arena football, other than the AFL signing a major network television broadcasting contract with NBC, was the development of the official Arena minor league, af2, beginning in 2000. This effort basically served two purposes: one as a developmental league for Arena and as a place where former collegiate players could develop while at the same time learning and becoming accustomed to the unique Arena rules, and secondly as a pre-emptive way of shutting out potential new indoor football competitors (this was especially important as the 2007 expiration of Foster's patent on the rebound nets approached). At times over forty teams participated in this league, almost uniformly in cities which also had minor league ice hockey teams and hence suitable arenas.
Shortly before the end of 2008, the Arena Football League announced that it would not be playing a 2009 spring season but that the play of its developmental league (af2) would continue as scheduled. During the previous few years, the league administrators and team owners had allowed player salaries and other costs to rise to the point where the league and many of the teams were losing a substantial amount of money. Late in the summer of 2009, with the team owners unable to agree on a plan for making the league viable again the AFL announced that it was folding.
The Arena Football 2 League played a successful 2009 season. Most of the teams made a sustainable profit and the team owners were eager to see the af2 continue for another year. However, as it became apparent that the AFL owners would not be able to adopt a workable business model, the af2 team owners found themselves facing a problem. With the AFL owning 50.1% of the af2, it would fold if the AFL folded. At the end of the 2009 season, a gathering of af2 and AFL team owners set out to form their own organization, originally known as Arena Football 1. AF1 went on to purchase all assets of the original AFL and af2, except for a few team names and logos owned by outside parties, in a December 2009 bankruptcy auction. Shortly after the purchase, AF1 adopted the Arena Football League name, and the reborn AFL began operations in 2010. The "iron man" rule, requiring at least six of the eight players to play on both offense and defense, was dropped, but most other past AFL rules remained unchanged. The league subsequently re-entered former AFL markets (some of which it has subsequently left again) and its teams took up the names of their markets' former teams; the Bossier City Battle Wings became the revived New Orleans VooDoo, the Alabama Vipers assumed the identity and history of the Georgia Force, the expansion Milwaukee Iron assumed the name and history of the Milwaukee Mustangs and the Philadelphia Soul franchise was revived for the 2011 Arena Football League season as well.
By the end of the 2017 season, almost all of the league's teams had either folded or suspended operations, with only the Philadelphia Soul having existed prior to 2016. Three expansion teams, all in the northeastern United States, have been established in that time frame to keep the league operational.
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As the AFL and af2 were having to deal with the fact that the AFL had overextended itself, two newer leagues were solidifying their positions in the world of indoor football, without the use of the rebound nets at the ends of the field. On October 19, 1998, Richard F. Suess (of the original Professional Indoor Football League) filed for and was subsequently awarded U.S. patent number 6,045,466 for his version of Indoor Football; Suess's proprietary version, which included rebound nets in the middle of the field instead of the ends, has never been played, and Suess never used rebound nets in the original PIFL.
The Indoor Football League (IFL) entered 2011 as the largest (in number of teams) of then currently-existing indoor leagues with 22. It began in the autumn of 2008 when two already-established leagues ( Intense Football League and United Indoor Football) chose to merge into a single organization. The IFL's expansion model has been based less on establishing brand-new teams and more on acquiring existing teams from other leagues. The IFL has continuously downsized since then and is playing the 2018 season with six teams.
Several other indoor leagues have been announced without ever actually commencing play, or operating only briefly with a handful of teams. Like the Arena Football League, all of these operations contemplated their playing season as being entirely or primarily outside the traditional fall/early winter season of the outdoor sport so as not to be competing with it directly for fan support. Some were claimed attempts to form a second "major" league of indoor football while others were strictly efforts to form a new "minor" league. The common factor for failing all seemed to share was serious undercapitalization.
Since the first non-arena indoor league (Professional Indoor Football League) began play in the 1998, there has often been a pattern of instability. Each off-season has seen teams jumping from league to league. In addition, leagues have annually merged, changed names, and separated. The organization that was most recently known as American Indoor Football (AIF) went through three names and two ownership changes in its first three seasons.
A few leagues have achieved a certain level of stability, though still many teams go from one league to another annually, both between each other and between regional and national leagues. As of the 2018 season, the aforementioned IFL and Champions Indoor Football (CIF), along with the American Arena League (AAL) and National Arena League (NAL), are slated to play. Both CIF and the AAL are mergers of existing leagues. The CIF was formed from a merger of the Champions Professional Indoor Football League and the Lone Star Football League in 2015. The AAL was formed in late 2017 as the combination of three leagues that each played one season: the Can-Am Indoor Football League, Arena Pro Football, and Supreme Indoor Football.
Many leagues have also been plagued with internal dissension. For example, the National Indoor Football League (NIFL) was characterized by annual issues between teams and league owner Carolyn Shiver before it folded after its 2007 season, the American Professional Football League (APFL) ended its 2006 season with a forfeit of the championship game when the league offices refused to allow the championship game to be hosted at the home of the team who had won the right to host and refused to play the game, and the Continental Indoor Football League (CIFL) had its defending champion Rochester Raiders quit the league in the middle of the playoffs in 2008.
The best-known indoor women's football league is the Legends Football League (formerly known as the Lingerie Football League). Known for its scantily-clad players and its signature event, the Legends Cup (formerly Lingerie Bowl), the LFL plays by a variant of indoor rules and played most of its games in indoor stadiums. The league's brief foray into Australia was played in outdoor stadiums; these teams nevertheless played under indoor football rules, and they and a few LFL-US teams that are either defunct or now play indoors are the only teams known to have played the indoor game outdoors. Otherwise, all other women's leagues play on outdoor fields with outdoor rules; there have been several other attempts to form indoor women's football leagues, but none have made it to play.
The Continental Indoor Football League, a traditionally men's league, earned a certain notoriety by being the first professional men's football league (indoor or outdoor) to employ female placekickers: Katie Hnida with the Fort Wayne FireHawks, and Julie Harshbarger with the league's oft-renamed Chicago franchise.
All current indoor football teams play at a minor league or even semi-professional level. The average player's salary in the Arena Football League was US$1,800 per game in 2008; this is about one-quarter of the Canadian Football League and the XFL (adjusted for inflation) and half the salary the United Football League was paying at the end of its lifespan in 2012. Players in af2 were paid $250 per game and the AIFA and IFL had per-game salaries of $200 per game; the current AFL paid $885 per game for most players in 2012, with that number rising to $940 per game in 2013 (although players then had to pay for their own housing, which the league previously provided); starting quarterbacks receive a $300 per game bonus.  As of 2012, the IFL pays $225 per game, with a $25 bonus for each win. 
Running back Fred Jackson rushed for over 1,000 yards as the starting running back for the 2009 Buffalo Bills, and his high quality play earned him a spot on USA Today's "All-Joe" Team. Jackson played the early part of his professional football career for the Sioux City Bandits now of Champions Indoor Football. Probably the most notable player to come out of Arena football into the National Football League is Kurt Warner, MVP quarterback of the Super Bowl XXXIV champion (2000 game, 1999 season) St. Louis Rams, who had previously quarterbacked the former Iowa Barnstormers of the AFL. The National Football League removed a ban that had been in place on any of its owners owning teams in any other sort of football operation with respect to Arena football only, and several of them had bought or started Arena teams at one point. However, the NFL allowed to lapse an option it had negotiated allowing it to purchase up to 49% of Arena football, and as of early 2007 seemed to have backed away from any plan it may have had to use Arena football as a developmental league in any sort of "official" sense, perhaps in the interest of not undermining its then-existing "official" developmental league, NFL Europa.
Several NFL owners owned Arena Football League teams in their own cities prior to the league's bankruptcy. At the end of the 2008 season, Jerry Jones and the Dallas Desperados (who had similar colors and logos to the Dallas Cowboys), Arthur Blank's Georgia Force, and the Colorado Crush (whose shareholders included Broncos owner Pat Bowlen and Rams then-minority owner Stan Kroenke) were still in the league. San Francisco 49ers owner Denise DeBartolo York and Washington Redskins owner Daniel Snyder had future expansion rights to their respective cities. Tom Benson's original New Orleans VooDoo and Bud Adams's Nashville Kats had already folded prior to the bankruptcy and none of the NFL owners with AFL franchises returned to the league after its reformation in 2010, and most favored abolishing the league entirely. 
Two players who have played at least the majority of one season in an indoor football league have reached the Pro Football Hall of Fame: 2017 inductee Kurt Warner played the first three seasons of his professional career in the AFL, and 2018 inductee Terrell Owens played his last professional season with the Indoor Football League in 2012.
Dozens of former and current professional outdoor football players also have invested money into indoor football franchises.
The following is a list of arena and indoor football leagues:
- "CHICAGO WINS BY A POINT: University Team Defeats Michigan for the First Time; INDOOR PLAY PROVES A SUCCESS; Coliseum Utilized and Twenty Thousand In Attendance—Herschberger of the Home Eleven Kicks His Way Into Fame". Nebraska State Journal. November 27, 1896.
- "Football Played Indoors". The New York Times. November 27, 1896.
- "THE FOOTBALL GAMES: Results on the Gridiron From Ocean to Ocean; INDOOR GAME AT CHICAGO; The University of Chicago Defeats the University of Michigan In a Hard Contest — Games Played at Other Points". Delphos Daily Herald. November 27, 1896.
- Carroll, Bob (1980). "The First Football World Series" (PDF). Coffin Corner. Professional Football Researchers Association. 2 (Annual): 1–8. Archived from the original (PDF) on 2010-12-15.
- "Bears vs. Spartans". Milwaukee Journal. United Press. December 18, 1932. p. 1B.
- Smith, Wilfrid (December 16, 1932). "Bears battle with Spartans moved indoors". Chicago Tribune. p. 25.
- "Bears, Spartans to play indoors". Milwaukee Journal. Associated Press. December 16, 1932. p. 7, part 2.
- "Pro gridders meet tonight in Windy City". St. Petersburg Times. Associated Press. December 18, 1932. p. 2, section 2.
- Dunkley, Charles W. (December 19, 1932). "Bears beat Spartans, 9-0; win pro title". Milwaukee Sentinel. Associated Press. p. 13.
- Williams, Marty (January 15, 1978). "Today's game not first indoors". Daily News. Bowling Green, Ohio. (Dayton Daily News). p. 12.
- Mayer, Larry (March 1, 2014). "Bears played NFL's first indoor game". Chicago Bears. Retrieved March 1, 2014.
- U.S. Patent 4,911,443 (filed September 30, 1987; parent application filed December 4, 1985; issued March 27, 1990)
- DiPaola, Jerry (June 19, 2012). "AFL players score hefty raise in new CBA". Trib Total Media. Retrieved 2014-03-18.
- "Terrell Owens scores three touchdowns. Indoor Football League". Yahoo! Sports. Yahoo!. Retrieved September 24, 2012.
- Hahn, John (2009-08-11). Who Really Killed the AFL?. OurSportsCentral.