From Bryan Garner’s Usage Tip of the Day: is it /mi-zuur-ee/ or /mi-zuur-ә/?
The pronunciation of this state name has provoked much strife. Although most Americans say /mi-zuur-ee/, many Missourians say /mi-zuur-ә/. In and around St. Louis, many say /ee/, but /ә/ has traditionally predominated in other parts of the state. Both pronunciations are standard. Yet it is a telling point that politicians running for statewide office are careful to say /ә/ — to seem folksy and avoid sounding like an auslander. But interestingly, the final-syllable /ә/ pronunciation seems to be for insiders only — all non-Missourians being expected to say /ee/. . . .In Illinois we have /lәr-nee/ (Lerna) and /lox-ee/ (Loxa) and no doubt /meh-nee/ others.
An early commentator, the noted linguist E.H. Sturtevant, attributed the final-syllable /-ә/ to hypercorrection. It’s a surprising but quite plausible argument: “In the dialect of Missouri and the neighboring states, final a in such words as ‘America,’ ‘Arizona,’ ‘Nevada,’ becomes y —‘Americy,’ ‘Arizony,’ ‘Nevady.’ All educated people in that region carefully correct this vulgarism out of their speech; and many of them carry the correction too far and say ‘Missoura,’ ‘praira,’ etc.” E.H. Sturtevant, Linguistic Change 79 (1917).
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