Which state is the city of Springfield from in the Simpsons?

The popular and long running show The Simpsons have intentionally left out from which state the home town of Springfield is with the intention of relating to everyone's Springfield.  There have been several references to possible states to keep fans guessing and has become part of the playful nature of the show.   Alas, in 2012, the show's creator revealed that it is based on Springfield, Oregon.