Book excerpt: A must-have for any true football fan, The Evolution of Professional Football is a one-of-a-kind source for the evolution of the National Football League since its inception in 1920. Unlike others, this almanac offers an accessible, easy-to-read format setting out the history of the league, its teams, and its champions. Learn about all the original NFL teams, such as the Dayton Triangles and the Minneapolis Mariners, along with yearly champions, key facts from each year, awards, and other "must-know" information for the true football fan.Additionally, this book offers a trove of stats and facts including Hall of Fame inductions, Super Bowl and playoff appearances, important changes in the rules of the game, and even an explanation of how the salary cap works. The Evolution of Professional Football is an essential addition to the library of any true fan.