| Code | Name | Region |
|---|---|---|
| USKAD | Oakland, Fayette | TN |
| USOFW | Oak View | CA |
| USYOB | Oakboro | NC |
| USOT2 | Oakbrook Terrace | IL |
| USOKQ | Oakdale | CA |
| USM8E | Oakdale | CT |
| USODH | Oakdale | IL |
| USODA | Oakdale | LA |
| USOKE | Oakdale | MN |
| USOQD | Oakdale | NY |
| USUXR | Oakdale | PA |
| USODD | Oakdale, Morgan | TN |
| USJYU | Oakes | ND |
| USKSE | Oakesdale | WA |
| USGKF | Oakfield | ME |
| USOK2 | Oakfield | NY |
| USKFL | Oakfield | TN |
| USOKF | Oakfield | WI |
| USK9F | Oakford | IN |
| USHK5 | Oakham | MA |
| USOHU | Oakhurst | CA |
| USODW | Oak Harbor | WA |
| USOQH | Oak Hill | FL |
| USFKH | Oak Hill | NY |
| USOAH | Oak Hill | OH |
| USKHJ | Oak Hill | WV |
| USOAV | Oak Hill, Fairfax | VA |
| USOHL | Oak Hill, Pittsylvania | VA |
| USOJH | Oak Hills | CA |
| USOAI | Oak Island | NC |
| USOKI | Oak Island | NJ |
| USOKL | Oak Lawn | IL |
| USQ8P | Oak Park | CA |
| USQOP | Oak Park | IL |
| USOPJ | Oak Park Heights | MN |
| USOPC | Oak Park, Oakland | MI |
| USKOI | Oak Point | TX |
| USOR4 | Oak Ridge | NC |
| USORE | Oak Ridge | NJ |
| USOKR | Oak Ridge | TN |
| USO3A | Oak Ridge North | TX |
| USNFU | Nursery | TX |
| USNUT | Nutley | NJ |
| USVGK | Nutting Lake | MA |
| USZNC | Nyac | AK |
| USNYX | Nyack | NY |
| USYEZ | Nye | MT |
| USNSZ | Nyssa | OR |
| USQA8 | Oak | NE |
| USOKP | Oak | PA |