Did you know that the Cardinals are the oldest team in American football history? They belonged to Chicago, were originally called the Morgan Athletic Club and were formed in 1898 by Chris O'Brien. Okay so if you're asking, "How can you say they're the oldest team if they weren't even the Cardinals?" Because the team has never been disbanded, only renamed and moved, so it's still the same team. Think of it like this; let us say you change your name and move to Scotland. You're still the same person.
Oh and by the way, that same year (1898) the rules were changed and a touchdown went from 4 points to 5. Just so you know. ;)
I'm not really a football fan, but I am a history nut. I find that very interesting. If you're like me, then I recommend downloading the NFL's official historic timeline, which is a free pdf. You can get it by clicking here.