800## ZIPs are in the Denver area. There is a Springfield in Colorado, though it’s a tiny town in the southeastern corner of the state.
Do any of them neighbor a Shelbyville?
Not to mention Capital City, Brockway, Ogdenville, North Haverbrook, Spittle County, Little Pwagmattasquaresmetport, Frigid Falls, Lake Flacid, Mt. Seldom…
One of the snowiest cities in the country is in AZ. Not near any port though.
Clearly its a universe where Bill Hicks/Tool got their wishes, an earthquake took out most of CA, and it’s the Arizona Bay.
But then West Springfield is bigger than Texas so maybe they skip the multi-day trip to locations in town.
The biggest blizzard I ever experienced was in Flagstaff, AZ. Granted my experience with snow is minimal.
I’ve always just assumed it was Groening’s home state of Oregon. Coastal, big mountains, settled after the Revolutionary War, not Southern, not too hot, no too cold…
I’ve also seen the explanation that it’s one of those Soviet fake American towns used to train spies, and the titular family are the only ones who don’t know that.
I disagree.
It will end when a new Associate Producer or Executive Vice President thinks “I have a better idea”, and said idea kills the series.
BTW–I do not watch that mess.
I used to.
I sympathize with my hypothetical mid level manager character. Who is not based on me at all. 
The Simpsons do live near saguaro cactus. So either they live in AZ, or the writers are as ignorant of the range of that cactus as every other Hollywood writer…ever.
(or it’s all for fun. I used to laugh that The Simpsons made fun of everyone. And then I hated the Grimey episode, until I realized I was the target this time: People that take it too seriously. That burned!)
They don’t care whose toes they step on!
The Grimes episode was Homer’s Enemy and it’s my favorite. Incidentally, I’ve heard the argument that all of the memorable, quotable episodes were from the first ten years or so and I think it’s true. Perhaps that’s because those were the episodes that were most widely watched, so they entered the national consciousness?
You think you hated it, I have a friend whose actual name is Frank Grimes.
Do you all call him Grimey? He likes to be called that.
I’m not American so I don’t have an informed opinion but that was always my guess too (and that’s without knowing Groening is from there). It just seems to fit with what I know about the state.
While it’s fun to speculate, the creators called it Springfield because of the old trope (which I think is false) that Springfield is the most common city name in the US
I’ve never been to Portland, Oregon, but I’ve heard that many street names inspired Simpsons character names, like Lovejoy, Quimby, Flanders and so forth.
This is correct
The answer to the OP’s question is “sometime between now and when the show becomes unprofitable.” But don’t take my word for it–here’s Troy McClure!
And that was more than thirty years ago.