and I thought I was a simpsons fan. Hahaha Well the real answer is that there isn't one. The real question is if there really was a state that they lived in what would it be. I would say melonhead gets the logical answer though. Who gets the answer from info from the show only. Let's gather all the info we can a tally them up and the one that comes on top will be our answer. Ready go.
There is a nuclear power plant in Springfield Illinois, I'm pretty sure. Also, next to springfield is shelbyville, and on the outskirts of springfield there are hillbillys. I also think it could be Oregon. Springfield was settled by settlers in white roofed wagons (like on the oregon trail), so it has to be somewhere where people could settle in like the 1800s. The town has a lake next to it (as does the one in Illinois), and I'm pretty sure there is a collage in springfield (there is a collage in the one in Illinois). Springfield has forest around it, I can't get anything off the google maps. I've watched the simpsons for along time, and seen so many of their episodes.
I found this site it gives some hints as to where it is http://www.snpp.com/guides/springfield.list.html#evidence
thats what my sister and i think, because they always say things like 'we have the lowest reading scores in this state' and in the episode someone mentione going 'south of the border' and homer said 'oh, you mean tennesee?' matt must have a state for the simpsons, because in the episode where they go to brazil, the boy lisa visited said he didnt know how to write to them because he didnt know what state they lived in, and lisa said 'its tricky, but if you look closely at the clues you can figure it out" lol i know i sound like a geek, but my sis and i have been simpson fans for years, and this is like 'our thing' to find out where they are from
i wouldnt put too much faith into landscapes, ive heard a lot of commentary and the directors and writers state over and over that the simpsons have 'their own universe', so they probably dont research on landscape or spend a lot of time on it. not every episode is written like its in a certain state, its just that once in a while theyll throw in a clue
Plus the show has had Springfield depicted as having a desert, ocean, mountains and cold enough winters for a blizzard. The "Behind the Laughter" episode had the Simpsons living in Kentucky but that was just that episode.
That may be because Matt Groening was from Oregon, I think. However, in an episode where Homer and Bart were on the road, they passed through Oregon.