| | O'Brien County | IA | 19141 | | | | | nonmetro county (rural) | farm-dependent | https://maps.google.com/?q=O'BrienCounty+IA |
| | Osceola County | IA | 19143 | | | | | nonmetro county (rural) | farm-dependent | https://maps.google.com/?q=OsceolaCounty+IA |
| | Page County | IA | 19145 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=PageCounty+IA |
| | Palo Alto County | IA | 19147 | | | | | nonmetro county (rural) | farm-dependent | https://maps.google.com/?q=PaloAltoCounty+IA |
| | Plymouth County | IA | 19149 | | Le Mars, IA 30180 | Sioux City-Le Mars,
IA-NE-SD 512 | Central | metro county (urban) | manufacturing-dependent | https://maps.google.com/?q=PlymouthCounty+IA |
| | Pocahontas County | IA | 19151 | | | | | nonmetro county (rural) | farm-dependent | https://maps.google.com/?q=PocahontasCounty+IA |
| | Polk County | IA | 19153 | | Des Moines-West Des
Moines, IA 19780 | Des Moines-West Des
Moines-Ames, IA 218 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=PolkCounty+IA |
| | Pottawattamie County | IA | 19155 | | Omaha, NE-IA 36540 | Omaha-Fremont, NE-IA 420 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=PottawattamieCounty+IA |
| | Poweshiek County | IA | 19157 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=PoweshiekCounty+IA |
| | Ringgold County | IA | 19159 | | | | | nonmetro county (rural) | farm-dependent | https://maps.google.com/?q=RinggoldCounty+IA |