As noted above, the question of why people sometimes think there are 52 states has been discussed on this board before. I find it a little eerie that this error seems to be so prevalent.
My WAG is that a good deal of the confusion arises from the number 52 being the number of weeks in a year and cards in a deck; people are just sort of used to it being a number of constituent parts. The suggestion above about how people tend to think of Alaska and Hawaii as a pair may well have something to do with it too.
Speaking as 47-year-old lifelong resident of the state, I can say with some confidence that “Mizzouruh” is a proper pronunciation. It also used to be the predominant one within the state. I recall that as late as the 1970s people did jokes about people saying “Mizzouree”; there was a financial institution in St. Louis, for instance, which ran a radio commercil in which a game show
host introduces a contestant as being from “St. Louieee Missoureee” and tells her she’s wrong when she gves the name of the institution "Mizzouruh So-and-So in St. Louis. He says the correct answer was “Mizzouree So-and-So in St. Louieee”.
I’ve read various times that historians are generally agreed that “Mizzouruh” is the older, more traditional pronunciation. Harry Truman invariably said “Mizzouruh”. Various broadcasters who are particularly exacting in their pronunciation invariably say “Mizzouruh”. One is Aliester Cooke. Another was John Chancellor.
It’s my WAG that the levelling effect of television, which has tended to standardize pronunciation and usage in the U.S., has caused the “Missouree” pronunciation to become more prevalent, even within the state. The fact that television endorses something does not, of course, make it “right”. Television also appears to be responsible for such oddities as the pronunciation of “shiekh” and “shake”, “often” as “off-ten”, and “forte” when meant in the sense of a personal strength, as “for-tay”. Maybe it will even have us all saying “sal mon” someday.
On that subject, while I never had a teacher tell me there were 52 states, my fourth grade teacher marked me wrong when I wrote that the Norwegian flag was “blue, white, and red”. The only correct answer, she insisted, was “red, white, and blue”. My seventh grade science teacher was convinced she had disproven the theory of evolution “because all of the monkeys haven’t evolved into people”. My high school American History teacher taught that slaves were never abused or subject to threats or coercion because they were expensive to buy. It could have been worse; a high school classmate swore that one of his grade school teachers told him that most black people in the United States were the descendants of people who rowed there from Africa in birchbark canoes.
Earlier this year I taught a class to paralegal students. Their textbook, published just last year, said there are 26 amendments to The U. S. Constitution.
While we’re at it, has anyone heard that “everyone knows” there are Twelve Commandments? I know Mel Brooks used this as a joke in History of the World, Part I, but I had heard this said before.