Mystery solved: The Simpsons are Oregonians.

Homer, Marge, Lisa, Maggie and Bartholomew JoJo "Bart" Simpson reside in the Springfield that's in the Beaver State, The Simpsons creator Matt Groening tells Smithsonian magazine, AP tells us.

Springfield, Ore., is 100 miles south of Portland, Groening's hometown.

"When I grew up, I realized it was just a fictitious name," he said. "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," he told the magazine.

Groening's revelation wasn't news in the inspirational Springfield.

"Oh, OK, we knew that," community-relations manager Niel Laudati told AP.

Springfield, Ore., made a pre-emptive strike in 2007 when Groening toured for The Simpsons Movie. The "proud Oregonian" Groening gave "the real Springfield" a signed plaque.

Here's what he said in a revealing interview with Smithsonian:

OK, why do the Simpsons live in a town called Springfield? Isn't that a little generic? 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. You've never said it was named after Springfield, Oregon, before, have you? 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."

Don't have a cow. We'll be scouting for reaction from some of the wannabe Springfields, so check back.

Update at 7:37 p.m. ET: Ahead of the 2007 movie, USA TODAY held a contest to pick the the Simpsons' "real" hometown. The Springfield in Vermont beat its Oregon counterpart and rivals from 12 other states.

BLOG: Pick the best Springfield

Springfield, Vt., got 15,367 votes, about 6,000 votes more than the town's population, our sister paper the Burlington, Vt., Free Press reminds us. The namesake in Illinois was runner-up, followed by Oregon and Massachusetts.

As a reward, Vermont's Springfield hosted the July 21 premiere at the Springfield Movie Theater on Main Street.

STORY: A 'Simpsons' frenzy in Springfield, Vt.

No official reaction yet from The City Formerly Known As The Hometown of The Simpsons.