Where, in North America, was Sinclair Lewis's "Winnemac" supposed to be?

"Winnemac" is a fictional location created by the Nobel Prize-winning American author Sinclair Lewis.

Harry Sinclair Lewis (7 February 1885 – 10 January 1951) was a novelist, short-story writer and playwright. In 1930, he became the first US writer to receive the Nobel Prize in Literature, which was awarded "for his vigorous and graphic art of description and his ability to create, with wit and humor, new types of characters." His works are known for their critical views of American capitalism and materialism in the 20th century. He was honoured by the US Postal Service with a postage stamp in the "Great Americans" series.

Lewis's best-selling novel "Babbit" -- along with several later works -- is set in a fictitious city "Zenith" in the equally fictitious Midwestern state of "Winnemac," supposed to be adjacent to Ohio, Indiana, Illinois, and Michigan. Lewis turned to the creation of a fictional locale after residents of Sauk Centre, Minnesota, were upset with the town's portrayal in Lewis's famous work "Main Street".