American football evolved in the United States, originating from the sport of rugby football. The first game of American football was played on November 6, 1869 between two college teams, Rutgers and Princeton, under rules resembling rugby and soccer. A set of rule changes drawn up from 1880 onward by Walter Camp, the "Father of American Football", established the snap, eleven-player teams and the concept of downs, and later rule changes legalized the forward pass, created the neutral zone and specified the size and shape of the football.
American football as a whole is the most popular sport in the United States; professional football and college football are the most popular forms of the game, with the other major levels being high school and youth football. The NFL's championship game, the Super Bowl, is the most popular single-day sporting event in the United States and among the most-watched club sporting events in the world.