here's some evidence you might like to read... (not on snpp.com)
[3F20]
-- Homer tells Apu that he may have to locate Springfield on the map for his citizenship. Homer can't find it, and just when Lisa points to the correct place, Bart blocks the view. The states that we cannot see (i.e. the states Lisa could be pointing to) are:
North Dakota, South Dakota, South Carolina, Florida, Nebraska, Kansas, Oklahoma, Texas, Louisiana, Arkansas, Missouri, Iowa, Minnesota, Wisconsin, Illinois, Michigan, Indiana, Kentucky, Ohio, Tenessee, Georgia, Alabama, Mississippi and New Mexico.
[AABF08]
-- Marge is on the phone, giving her address to the egg company: "742, Evergreen Terrace, Springfield. O, hi-o Maude, come on in!" (Ohio)
[BABF16] -- After the family vacation, OFF say that they are only welcome in Florida and North Dakota. Homer says that Florida smells, and the family are only left with North Dakota. They are welcome in their own state, so it must be one of these two (most likely North Dakota)