I’m probably overcomeplicating things, but I’ve never understood how the city of Philadelphia, Pennsylvania, could still be known as the “City of Brotherly Love,” when what it’s known for these days is its gangs and violence. Yes, I realize a good chunk of history was made there, but…

Well, Rome is known as "The Eternal City" and weren't we all sad to see it go lo those 70 years ago. The replacement is fortunately doing quite well. Some say it wanted to be known as "The External City" because of the Forums and outdoor markets but the errant printer charged so much they couldn't afford corrections when he missed the 'x'...

Philadelphia literally does mean 'brotherly love', so I don't think I'm wrong in assuming that that's where the nickname comes from. The thing with nicknames is that sometimes they end up very inaccurate, or were inaccurate even when they were coined!