Gridiron football, or North American football, is a form of football primarily played in the United States and Canada. The predominant forms of gridiron football are American football and Canadian football.
The term "gridiron" originated as a description of the sport's then-characteristic playing field, which, until the late 1910s–early 1920s, was marked with a series of parallel lines in a checkerboard (or grid) pattern, resembling a gridiron. The grid system was abandoned in favor of the system of yard lines and hash marks used today, but the term "gridiron" has survived.
Gridiron football developed in the late 19th century out of the original games now known as rugby football and association football. It is distinguished from other football codes by its use of hard plastic helmets and shoulder pads, the forward pass, the system of downs, a line of scrimmage, more specialist positions and formations, free substitution, platooning of different players for offense and defense, measurements in yards, a distinctive brown leather ball in the shape of a prolate spheroid with pointed ends, and the ability to score points while not in possession of the ball by way of the safety. Walter Camp is credited with creating many of the rules that differentiate gridiron football from its older counterparts.
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