The answer? Oregon.
Not a total shock, considering Groening grew up in Portland, Ore. But still, the cartoonist has been awfully cagey about the location over the years.
But in a detailed Q&A in the May 2012 issue of Smithsonian magazine, Groening has finally come clean, telling interviewer Claudia De La Roca, "Springfield was named after Springfield, Oregon. The only reason is that when I was a kid, the TV show 'Father Knows Best' took place in the town of Springfield, and I was thrilled because I imagined that it was the town next to Portland, my hometown. When I grew up, I realized it was just a fictitious name. I also figured out that Springfield was one of the most common names for a city in the U.S. In anticipation of the success of the show, I thought, 'This will be cool; everyone will think it’s their Springfield.' And they do."
So why did Groening keep it a secret for so long? "I don’t want to ruin it for people, you know? Whenever people say it’s Springfield, Ohio, or Springfield, Massachusetts, or Springfield, wherever, I always go, 'Yup, that’s right.'"
Well, now the secret is out.
There are Springfields in 22 states, so it's been easy for anyone to see "The Simpsons'" Springfield as their Springfield. And the show has thrown all kinds of contradictory geographic clues at the viewers over the years, with the town being close to a desert, a volcano, a glacier and several national parks.
In "The Simpsons Movie," Simpson family neighbor Ned Flanders tells Bart that the states bordering Springfield's home state are Ohio, Nevada, Maine and Kentucky.
Now the only "Simpsons" question remaining: How many more episodes will the show, which recently passed episode 500, go?
-- Patrick Kevin Day