Since moving into the Philadelphia area, I’ve bought and often wear Eagles-branded clothes. I have a Super Bowl LII T-shirt, an Eagles windbreaker and a cap, which I wear most often.
Invariably, whether I’m out shopping, eating at a fast-food joint or even walking in the woods, somebody spots the cap and says, “Go birds!”
I’ve lived in several NFL markets — Cleveland (Browns), Milwaukee (Packers), Seattle (Seahawks), San Francisco-Oakland (49ers/Raiders), and northern New Jersey (Giants). Only here in central Jersey (yes, it exists) do I regularly get hailed by fellow fans of the home (or nearly so) team.
That’s not to say I wouldn’t hear an occasional. “Go Browns” or “Go Niners,” but not to the extent I hear “Go birds.” That speaks to the passion of the Eagles fans, who are widely known for their devotion to the team, sometimes to extremes (Google “Eagles fans Santa”).
Fans of the original Browns franchise were extremely loyal, although I was long gone from town when the Dawg Pound came to be. I’ve never much cared for it, frankly, but those involved seem to love it.
I had season tickets to the Seahawks for six years through work, and fans were relatively sedate, possibly oppressed and depressed by the dreary Kingdome ceiling. I’m surprised that they now have a “12th man” persona.
While living in Alameda, California, during a few of the years when the Raiders returned from Los Angeles and had there headquarters there, I don’t recall owning any silver-and-black regalia. Having worked a concession stand at the Oakland-Alameda County Coliseum one freeway exit from home, I can verify that if any team’s fans can out-crazy the Eagles’ fans, it is the Raiders’ fans.
The biggest rivalries I’ve experienced are, in increasing intensity, Packers-Bears (I lived outside Chicago for a while, too), Eagles-Cowboys and Browns-Steelers.
We all have teams we love and teams we hate. For now and the foreseeable future, I’m going with the birds.
The Ball Caps Blog 
I have no doubt about the passion of Philly fans, but I think one reason you get such a reaction in central NJ, is that the loyalties are so divided among the NY and Philadelphia markets. Fans are more likely to react because they probably see Philly represented less often. Just a theory… It’s sort of the same when you live in Central Connecticut where the Yankees-Red Sox rivalry splits the fan base.
Good point. The Costco in Lawrence and Kohl’s in Hamilton stock only Eagles gear, although the “Princeton” Target in West Windsor carries Eagles and Giants. We’re definitely in crossover territory. Head north toward New Brunswick and the stores quickly switch to the Giants. I had a Jets shirt back in my Summit days, so their stuff must be up north.