| Code | Name | Region |
|---|---|---|
| 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 |
| USUNK | Unalakleet | AK |
| USUAA | Unalaska | AK |
| USUVL | Uncasville | CT |
| USUH2 | Underhill | VT |
| USUWD | Underwood | IA |
| USUND | Underwood | ND |
| USUDD | Underwood | WA |
| USUDF | Uneeda | WV |
| USUCO | Unicoi | TN |
| USUOM | Union | IA |
| USUNZ | Union | IL |
| USYNR | Tyner | NC |
| USTG2 | Tyngsboro | MA |
| USTYE | Tyonek | AK |
| USTYJ | Tyro | VA |
| USTYF | Tyrone | GA |
| USTYB | Tyrone | NM |
| USXNK | Tyrone | PA |
| UST9Y | Tysons Corner | VA |
| USUBY | Ubly | MI |