| Code | Name | Region |
|---|---|---|
| USSKH | Smithville | AR |
| USSMI | Smithville | GA |
| USXT8 | Smithville | MS |
| USYSM | Smithville | TN |
| USS2V | Smithville, Bastrop | TX |
| USQSM | Smithville, Ritchie | WV |
| USIHV | Smithville, Wayne | OH |
| USQSQ | Smock | PA |
| USKTW | Smoketown | PA |
| USSVT | Slippery Rock | PA |
| USNN6 | Sloan | NV |
| USOTB | Sloatsburg | NY |
| USUXM | Slocum | RI |
| USSK4 | Smackover | AR |
| US8PT | Small Point | ME |
| USRQA | Smarr | GA |
| USSDB | Smartt | TN |
| USYSV | Smelterville | ID |
| USTTH | Smethport | PA |
| US8YK | Smith | KY |
| US9SC | Smith Center | KS |
| USSCJ | Smith Cove | AK |
| USIXR | Smith River | CA |
| USSM5 | Smithfield | IL |
| USSDE | Smithfield | KY |
| USS9I | Smithfield | ME |
| USSMF | Smithfield | NC |
| USUYV | Smithfield | OH |
| USSF3 | Smithfield | PA |
| USXSL | Slater | CO |
| 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 |