| | | Muskegon County | MI | 26121 | | Muskegon-Norton Shores,
MI 34740 | Grand Rapids-Wyoming, MI 266 | Central | metro county (urban) | manufacturing-dependent | https://maps.google.com/?q=MuskegonCounty+MI |
| | | Newaygo County | MI | 26123 | | | | | nonmetro county (rural) | recreation | https://maps.google.com/?q=NewaygoCounty+MI |
| | | Oakland County | MI | 26125 | Warren-Troy-Farmington
Hills, MI 47664 | Detroit-Warren-Dearborn,
MI 19820 | Detroit-Warren-Ann Arbor,
MI 220 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=OaklandCounty+MI |
| | | Oceana County | MI | 26127 | | | | | nonmetro county (rural) | recreation | https://maps.google.com/?q=OceanaCounty+MI |
| | | Ogemaw County | MI | 26129 | | | | | nonmetro county (rural) | recreation | https://maps.google.com/?q=OgemawCounty+MI |
| | | Ontonagon County | MI | 26131 | | | | | nonmetro county (rural) | recreation | https://maps.google.com/?q=OntonagonCounty+MI |
| | | Osceola County | MI | 26133 | | | | | nonmetro county (rural) | manufacturing-dependent | https://maps.google.com/?q=OsceolaCounty+MI |
| | | Oscoda County | MI | 26135 | | | | | nonmetro county (rural) | federal/state
government-dependent | https://maps.google.com/?q=OscodaCounty+MI |
| | | Otsego County | MI | 26137 | | | | | nonmetro county (rural) | recreation | https://maps.google.com/?q=OtsegoCounty+MI |
| | | Ottawa County | MI | 26139 | | Grand
Rapids-Wyoming-Kentwood,
MI 24340 | Grand Rapids-Wyoming, MI 266 | Outlying | metro county (urban) | manufacturing-dependent | https://maps.google.com/?q=OttawaCounty+MI |
