What is the setting of Illusions: The Adventures of a Reluctant Messiah by Richard Bach?

The Adventures of a Reluctant Messiah is set in various locales in the American Midwest, some time in the second half of the twentieth-century, long enough after 1930, as it is mentioned several times that spare parts for antique biplanes are difficult to find. In the rural setting, radio is mentioned but no more modern means of communications - or commercial flying, for that matter.