It's been one of the best kept secrets in television history, but now Matt Groening has finally let the cat out of the bag by revealing which Springfield inspired 20 years of The Simpsons.

Matt Groening told Smithsonian magazine that he based the town on Springfield, Oregon. He believed the name would be perfect because it's so common – so everyone could and would believe it was their local town.

Springfield Oregon, which is 100 miles south of Groening's home town of Portland, has already incorporated the Simpsons into local lore. The Springfield Museum features a couch similar to the animated one shown in the show's opening credits, and a plaque marking the movie's release.

However, The Springfield depicted in The Simpsons is not always a flattering portrait. The school is falling apart, there is a constant fire at the town dump and the mayor is helplessly corrupt.

Niel Laudati, Springfield community relations manager, said: "We don't dwell on the bad stuff. Obviously we don't have a nuclear power plant. We don't have a lot of stuff in the Simpsons. What we do have are a lot of blue-collar working families that go to church every week and eat dinner together. That is accurate."

The Simpsons has been on the air for more than 20 years, becoming the longest-running American sitcom, the longest-running US animated programme and a cultural phenomenon.

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