Editing Rugby football (section)

=== Gridiron football ===
In [[Canadian football|Canada]] and the [[American football|United States]], rugby developed into [[gridiron football]]. During the late 1800s (and even the early 1900s), the two forms of the game were very similar (to the point where the United States was able to win the gold medal for rugby union at the [[Rugby union at the 1920 Summer Olympics|1920]] and [[rugby union at the 1924 Summer Olympics|1924]] Summer Olympics), but numerous rule changes have differentiated the gridiron-based game from its rugby counterpart, introduced by [[Walter Camp]] in the United States and John Thrift Meldrum Burnside in Canada. Among unique features of the North American game are 
* the separation of play into [[down (American football)|downs]] instead of releasing the ball immediately upon tackling
* the requirement that the team with the ball set into a [[formation (American football)|set formation]] for at least one second before [[snap (football)|resuming play after a tackle]] (and the allowance of up to 40 seconds to do so)
* the allowance for one [[forward pass]] from behind the site of the last tackle on each down
* longer play periods
* the evolution of hard plastic equipment (particularly the [[football helmet]] and [[Shoulder pads (sport)|shoulder pads]])
* a smaller and pointier ball that is favorable to being passed but makes [[drop kick]]s impractical
* a generally smaller and narrower field measured in customary units instead of metric (in [[Indoor American football|some variants of the American game]] a field can be as short as 50 yards between end zones)
* a distinctive field (shaped like a gridiron, from which the code's nickname is derived) with lines marked in five-yard intervals
Worldwide, there are two major professional leagues of gridiron football, both domestic:

* [[National Football League]]:
** {{Flagicon|USA}} [[United States]] (32 teams)
* [[Canadian Football League]]:
** {{Flagicon|Canada}} [[Canada]] (9 teams)