It wasn’t so long ago that folks in Rumford and Mexico scoffed at the notion that Mountain Valley and Cape Elizabeth had a rivalry.

A few years ago, I heard Jim Aylward refer to the Capers as “our so-called rivals,” not as a slight to the Capers, who were still new to the Campbell Conference at the time, but as a tip of the cap to the likes of Wells and York, with whom the Falcons have been locking horns for over two decades.

I also heard football fans, Falcon followers and neutral observers alike, and even cynical media types, mock the admittedly presumptuous title of Kirk Wolfinger’s documentary chronicling the 2007 season “The Rivals.”

Certainly, a documentary does not a rivalry make. If anything, you should be a bit suspicious whenever the media labels any game a rivalry without some evidence. Us media lowlifes have done our part in corrupting the use of the word. A couple of weeks ago, I saw a cable show devoted to the “rivalry” between the New England Patriots and Oakland Raiders, two teams that have never played in the same division and have met a grand total of three times in the playoffs in 50 years.

But there is no debate now. Mountain Valley vs. Cape Elizabeth is a football rivalry, one of the best football rivalries in the state. And not because the man I alternate this space with declared it No. 5 in the state in last week’s “Fab Five.” When the Falcons and Capers meet Friday night in the Campbell Conference semifinals, another chapter will be written, and it will be even more difficult to deny this is, indeed, a rivalry.

For the few remaining holdouts, I present the following:

Familiarity: The Falcons and Capers are more familiar with each other than any two teams in the state. This is the fifth time in the last six years they have played each other twice in the same season.

Stakes: Regular season or playoffs, Cape/Mountain Valley usually has a lot on the line. In 2006, 2007 and 2008, whoever won the regular season finale between the two teams earned home field advantage in the playoffs. From 2006 to 2009, they played for the conference championship and the right to play for the state title. And if you’ve seen “The Rivals” (and if you haven’t, you should), you know pride is always at stake, too.

Competition: Since 2006, the Falcons are 7-3 against the Capers, 4-1 in the playoffs. That may seem a bit lopsided on paper, but consider the context. The only other Campbell Conference teams to beat Mountain Valley during that time were York, which has done it twice, and Wells, which did it this year. Both of those teams would take a .300 winning percentage against the Falcons.

Dominance: You can’t have much of a rivalry if one team is dominant and the other struggles to tread water. But if you have two dominant programs over a period of time meeting on a regular basis during that period, you have the foundation of a rivalry (think Patriots/Colts). Since 2006, Mountain Valley is 62-6, Cape Elizabeth is 52-12. Aside from Lawrence and Bangor in the PTC, no two teams have ruled a conference so thoroughly in the last six years.

Passion: This was perhaps the first evident element of this rivalry. Of course, it first derived from with the cliched story line involving teams from two disparate communities, one blue collar, one white collar. That tension remains, but as time has passed and the Capers have proven themselves worthy adversaries on the field, that has faded more into the background. More and more, every meeting is about football and each team’s place among the hierarchy, not just in Class B but the state. Both teams look as the game as an opportunity to prove themselves, to each other and to everyone else.

Controversy: Any good rivalry has to have controversy to flare up tensions. We’re only two weeks removed from the most recent example involving these two at Cape’s Hannaford Field. There was a dubious change of possession ruling by the officials after a late Mountain Valley fumble, then some even more dubious timekeeping as Cape was trying to drive for the game-tying score in the final minute. Falcons fans were still upset with the officiating and the timekeeper long after victory was assured by a late defensive stand. I loved every minute of it, but I was the only one in the stadium with my blood pressure under control.

Drama: Several things contribute to drama besides the factors listed above — the competitiveness of the game, the setting and the crowd atmosphere. The games haven’t always been close, but when they are, they are as good as Maine high school football has to offer. As for the setting, like the rivalry itself, Mountain Valley had it all over Cape in the early days. Hosmer Field (now Chet Bulger Field) has been and always will rank among the best places to watch a game. Because Cape Elizabeth is relatively new to football, it’s taken some time for  Hannaford Field to make some headway. Two weeks ago, though, the Capers had one of the best student sections I’ve seen at any high school sporting event recently (even though they were a little too caught up in soccer chants).

Whether that meets your litmus test for a rivalry or not, there is no denying Cape/Mountain Valley is one of the best games to see this week.

We’ve got a lot of rivalries on the semifinal schedule. Some are based on geography, some on history, some on bad blood. Many go back a lot further than this one. But I guarantee that if someone did a statewide survey on which game fans would most want to see, Deering/Cheverus is the only one that would come close in the final results.

Someone is going to regret not being in Rumford on Friday night. It may even be me.