While baseball was once considered America's sport, those days are over, and now it is football that dominates the narrative.
One reason is that seasons are short - just five months long if you support a team that is fortunate enough to get to the play-offs. That means that, unlike baseball or basketball, every game matters, especially as the league is structured so that often the same teams meet twice a season.
That is enough in itself for rivalries to arise, but there can also be deeper, more complex reasons related to geography, history, culture, and world viewpoints.
Sometimes, there is no apparent logic to a rivalry. How do you explain why the Bills fans, based in Buffalo, feel such hatred for the supporters of the Miami Dolphins, based at the other end of the country? The two cities could not be less similar in terms of climate, lifestyle, and outlook. Or the antipathy between the Dallas Cowboys and the Washington Commanders - although everybody outside Dallas hates the Cowboys.
In other cases, rivalry on a football field is just the sporting manifestation of longstanding differences between cities and regions. What helps perpetuate any rivalry are the numerous controversial incidents that occur when these two teams meet, some of which may be lost in the mists of time but are passed down in the collective memories of fans as if they happened just yesterday.
There are those illegal hits, controversial calls, fumbles, last-gasp receptions, and field goals that are still celebrated even if the only reminders of them are some grainy YouTube videos. And there is no shortage of trash-talking from ex-players, coaches and fans thrown into the mix as well.
The most intense rivalries can also endure despite the best efforts of others to interrupt them. When Cleveland found itself without a football team in the mid-1990s, when the team owner moved the franchise lock, stock and barrel to Baltimore, it was the fans of their bitter rivals, the Pittsburgh Steelers, who did as much as anybody to see an NFL franchise reestablished for their neighbors.
Raiders fans, meanwhile, have seen the team move from Oakland to Los Angeles and now to Las Vegas, but that has done little to change how they feel about the Kansas City Chiefs.
This book concentrates on some of the most intense of those rivalries, exploring the reasons for them and the incidents that have helped fan the flames over the years.
Find out:
* Why cheeseheads and FISHTABs are not mutual terms of affection in Wisconsin and Chicago, respectively?
* How did one big victory by the Kansas City Chiefs almost lead to the death of a beloved horse?
* Who are the biggest heroes and the greatest villains as far as some teams are concerned?
* What is a bounty in the NFL, and who earned it for what?
Richmond Webb, a linesman with the Miami Dolphins, once said, "I don't know how it started, but these two teams don't like each other."
He could have been talking about any of the rivalries in this book.