Yep, Iowa City, Johnson County. When in doubt, always pick the place with the more selective university. :) So you didn't pick up on my Michigan hint eh?
There is a huge Dutch Reformed connection to Sioux Co. Iowa, Pella, Iowa, and the Grand Rapids, MI area...Holland, MI., Zeeland, New Holland, Hudsonville, et al...
My wife is Dutch (even had Vander in front of her maiden name ;-)...she grew up and went to school in Sioux Center Iowa, and her grandparents lived their whole lives in the predominately Dutch area you describe in Michigan.