I never thought about this before, although I'm sure others have, but the world's longest running TV comedy - The Simpsons - is famously located in Springfield. Although in all these years, they've never explained exactly where Springfield is. 

But then I realized that the town has its own radio station - whose jingle goes "No sports, no rock, no information; for mindless chatter, we're your station." The call letters are famously KBBL, so while that still doesn't specifically say where the town is, it certainly must be out west somewhere, since otherwise it would have been given a "W" designation. 

We've also seen winter come to Springfield, which means it's likely to be somewhere in the Northwest or in a place that's not summer all year round. According to this article, published in 2012, creator Matt Groening actually gave up the secret location in an interview - he maintains it's Springfield, Oregon, not far from the city of Portland, where he grew up. 

And that would fit a radio station with a "K" designation. So is the 30-year-old plus mystery finally solved? Probably not, but at least KBBL means we know where it isn't.