| | Allamakee County | IA | 19005 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=AllamakeeCounty+IA |
| | Appanoose County | IA | 19007 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=AppanooseCounty+IA |
| | Benton County | IA | 19011 | | Cedar Rapids, IA 16300 | Cedar Rapids-Iowa City,
IA 168 | Outlying | metro county (urban) | nonspecialized | https://maps.google.com/?q=BentonCounty+IA |
| | Boone County | IA | 19015 | | Ames, IA 11180 | Des Moines-West Des
Moines-Ames, IA 218 | Outlying | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=BooneCounty+Iowa |
| | Bremer County | IA | 19017 | | Waterloo-Cedar Falls, IA 47940 | | Outlying | metro county (urban) | nonspecialized | https://maps.google.com/?q=BremerCounty+IA |
| | Buchanan County | IA | 19019 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=BuchananCounty+IA |
| | Carroll County | IA | 19027 | | Carroll, IA 16140 | | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=CarrollCounty+IA |
| | Cass County | IA | 19029 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=CassCounty+IA |
| | Cedar County | IA | 19031 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=CedarCounty+IA |
| | Cerro Gordo County | IA | 19033 | | Mason City, IA 32380 | | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=CerroGordoCounty+IA |