More importantly, is it Missou-ree, or Missou-rah?
answer from their alumni website:
Some say Missour-ee, others say Missou-rah, but neither pronunciation of the 24th state's name is definitively correct, according to Charles Gilbert Youmans, professor emeritus in the College of Arts and Science's department of English at the University of Missouri. Youmans says that the history of the Show-Me-State's pronunciation intertwines with the indigenous, English and French cultures that have lived in the region.
"The name Missouri, meaning 'people of the big canoes,' or something similar, was applied to the local Native Americans by a neighboring tribe," said Youmans. "This was not what the 'Missourians' called themselves. Evidently, French explorers were the first Europeans to use the word Missouri, and English speakers borrowed it from the French. This is probably the source for the Missour-ee pronunciation, since that is how French speakers would pronounce the final-i. Based upon the French spelling, my guess is that the 'original' French pronunciation of the name would have been something like 'Missooree.'"
Youmans referenced the work of the late George Pace, another MU English professor, to explain how the Missou-"rah" pronunciation originated. The Missou-ruh pronunciation evolved from a spelling-based English pronunciation, Missour-eye, according to Pace's research. Eventually, the final lightly stressed syllable "eye" shrank to "uh." The "uh" sound is the default vowel for unstressed syllables in English, according to Youmans.
The pronunciation of Missouri has further variances besides its final syllable.
"To complicate matters, there is also variation in the pronunciation of the medial -ss- which a minority of Missourians pronounce as 's,' the way nearly all English speakers do with other double-s words such as Mississippi," said Youmans. "However, most people pronounce the -ss- in Missouri as 'z.' The pronunciation of the -ou- vowel also varies."
Charles Gilbert Youmans is the author of articles on verse, meter, dialectology, and discourse analysis in books and journals such as Language, Style, Neophilologus, American Speech, and Empirical Studies of the Arts. He has served as an executive committee member of the General Linguistics Group and the Division of Language and Society of the MLA. He has also served as chair of MU's Faculty Council, and has directed dissertations on prosody and stylistics.
