| Code | Name | Region |
|---|---|---|
| USAI9 | Slater | IA |
| USSVM | Slater | MO |
| USSQX | Slater | SC |
| USSLV | Slatersville | RI |
| USRI8 | Slaterville | RI |
| USSVP | Slatington | PA |
| USXME | Slaton | TX |
| USUHT | Slaughter | LA |
| USG9H | Slaughter Beach | DE |
| USSY8 | Slayton | MN |
| USFLQ | Sledge | MS |
| USSI2 | Sledge Island | AK |
| USSYE | Sleepy Eye | MN |
| USSO3 | Sleepy Hollow | NY |
| USSH9 | Sleepy Hollow Manor | NY |
| USSLQ | Sleetmute | AK |
| USUYN | Slidell | LA |
| USIGE | Slinger | WI |
| USZXS | Slingerlands | NY |
| USSGY | Skagway | AK |
| USKNE | Skaneateles | NY |
| USKAF | Skaneateles Falls | NY |
| USTKQ | Skiatook | OK |
| US7SK | Skidmore | MO |
| USSQM | Skillman | NJ |
| USSP3 | Skippack | PA |
| USSKP | Skippers | VA |
| USSOK | Skokie | IL |
| USSH5 | Skowhegan | ME |
| USKVQ | Skull Valley | AZ |
| USKUE | Skull Valley | UT |
| USSKW | Skwentna | AK |
| USS5K | Skykomish | WA |
| USUYZ | Skyland | NC |
| USSVK | Slate Hill | NY |
| USZTD | Slatedale | PA |
| USSI4 | Six Mile | SC |
| USSXM | Sixela | NM |
| USKSX | Sixes | OR |
| USIMC | Sims | NC |
| USSIO | Simsboro | LA |
| USSZU | Simsbury | CT |
| USSC7 | Sinclair | WY |
| USIGR | Singer | LA |
| USSIN | Singer Island | FL |
| USSKS | Sinking Spring | PA |
| US2SI | Sinton | TX |
| USSNT | Sioux Center | IA |
| USSUX | Sioux City | IA |
| USFSD | Sioux Falls | SD |