| Code | Name | Region |
|---|---|---|
| USSRJ | Sunbury | PA |
| USSKQ | Suncook | NH |
| USSD5 | Sundance | UT |
| USSUC | Sundance | WY |
| US5SR | Sunderland | MA |
| USV87 | Sunderland | VT |
| USS5E | Sunfield | MI |
| USJWR | Sunflower | MS |
| USSND | Sunland | CA |
| USXSP | Sunland Park | NM |
| USSM3 | Sunman | IN |
| USXSU | Sunny Isles | FL |
| USSUT | Sunny Point | NC |
| USYUY | Sunny Side | GA |
| USSUY | Sunnyside | WA |
| USSS6 | Sunnyside, Queens | NY |
| USUNP | Sunnyslope | ID |
| USSNN | Sunnyvale | CA |
| USSVD | Sunnyvale | TX |
| USUOL | Sunol | CA |
| USS5U | Sumner | MS |
| USUMN | Sumner | TX |
| USXMH | Sumner | WA |
| USS5N | Sumneytown | PA |
| USUAL | Sumrall, Lamar | MS |
| USSSC | Sumter | SC |
| USUMV | Sumterville | FL |
| USSCI | Sun City | AZ |
| USXZI | Sun City | CA |
| USSJY | Sun City | FL |
| USUNY | Sun City | KS |
| USSPE | Sun Prairie | WI |
| USSUO | Sun River | OR |
| USSVY | Sun Valley | CA |
| US5SV | Sun Valley | ID |
| USJUV | Sun Valley | NV |
| USKEP | Sunapee | NH |
| US7SM | Sunburst | MT |
| USSRZ | Sunbury | OH |
| USUMM | Summit | AK |
| USSMZ | Summit | AL |
| USXMV | Summit | IL |
| USITG | Summit | IL |
| US2MM | Summit | MS |
| USUYX | Summit | NJ |
| USSZS | Summit | PA |
| USAAO | Summit | SC |
| USSWP | Summit Point | WV |
| USSM9 | Summit Station | PA |
| USVVL | Summitville | IN |