| Code | Name | Region |
|---|---|---|
| USYUP | Upper Brookville | NY |
| USUDP | Union Dale | PA |
| USYUG | Union Gap | WA |
| USA8L | Union Grove | AL |
| USXUG | Union Grove | NC |
| USUGR | Union Grove | WI |
| USUH7 | Union Hall | VA |
| USQUP | Union Point | GA |
| USUSC | Union South Carolina | SC |
| USUSP | Union Springs | AL |
| USUSN | Union Springs | NY |
| USUOI | Union, Franklin | MO |
| USUIO | Union, Monroe | WV |
| USXUI | Union, Neshaboa | MS |
| USUOD | Uniondale | NY |
| USUT2 | Uniontown | KY |
| USUOO | Uniontown | OH |
| USUTN | Uniontown | PA |
| US7UN | Unionville | CT |
| USU2V | Unionville | MI |
| USUOV | Unionville | MO |
| USUN7 | Union | KY |
| USYUN | Union | ME |
| USUNX | Union | MI |
| USUKO | Union | MO |
| USUNH | Union | MS |
| USUON | Union | NJ |
| USUNI | Union | PA |
| USUCS | Union | SC |
| USUN8 | Union | WA |
| USUNA | Union Beach | NJ |
| USUNB | Union Bridge | MD |
| USZUC | Union Center | WI |
| USUNC | Union City | CA |
| USUCG | Union City | GA |
| USUNO | Union City | IN |
| USUCI | Union City | MI |
| USUC9 | Union City | MO |
| USUCJ | Union City | NJ |
| USUNN | Union City | PA |
| USUCY | Union City | TN |
| USZLQ | Ulysses | PA |
| USUML | Umatilla | FL |
| USUMA | Umatilla | OR |
| USUMT | Umiat | AK |
| USUMB | Umnak Island | AK |
| USUMP | Umpire | AR |
| US9QA | Umpqua | OR |
| USUDL | Unadilla | GA |
| USUNW | Unadilla | NY |