Homer's driver's license reads Springfield, NT 49007.
Homer's social security number is 568-47-0008. Social security numbers that begin with 568 are typically issued in California.
In "Mr. Lisa Goes To Washington," Springfield's congressman, Bob Arnold, is approached by two different shady corporate types and offered bribes, firstly to cut down Springfield's National Forest, and secondly, later in the episode, to drill for oil on Mount Rushmore. This places Springfield firmly in South Dakota.
Locate states that enforce capital punishment by electrocution, referring to "Bart the Murderer."
Remember that Springfield has its own international airport.
Search for a state that boasts a large gorge, such as in "Bart the Daredevil."
Springfield has its own docks and beach.
Where It Stands
In the May 2012 of Smithsonian Magazine, Matt Groening revealed that Springfield is located in his home state of Oregon.
In 2007, Twentieth Century Fox held a contest for cities of Springfield to prove their love for The Simpsons on video. The winner, Springfield, Vt., beat out 13 other Springfields across the country. That Springfield won the honor of hosting the hometown premiere of The Simpsons Movie. Videos were posted on USA TODAY's website, where readers voted for their favorite.
But Springfield is anywhere you want it to be. There is enough evidence in the hundreds of episodes of The Simpsons to preclude Springfield's placement in any specific American state. There are so many geographical contradictions between episodes that it is impossible for Springfield to actually exist somewhere real.