<human>:  What's the history of American Football?
<bot>: American football can trace its roots back to early versions of rugby and association football. The modern version of American Football was first developed in the 19th century and became popular in the early 20th century. It originated from the sport of rugby football, and is based on rules developed in 1876 by Walter Camp, considered the "Father of American Football". In the late 1800s, teams began using the forward pass, which further opened up the game. The game experienced a significant overhaul in the 1940s when the NFL was founded and a standardized set of rules became the norm. Over the next few decades, the NFL continued to grow in popularity. Today, American Football is the most popular sport in the United States and is followed by millions of people around the world.