| Signal Hill, CA (City) |
| Signal Mountain, TN (Town) |
| Sigourney, IA (City) |
| Sigourney Township, IA (Township) |
| Sigurd, UT (Town) |
| Sikes, LA (Village) |
| Sikes, ND (Township) |
| Sikeston, MO (City) |
| Silas, AL (Town) |
| Siler City, NC (Town) |
| Silerton, TN (Town) |
| Siletz, OR (City) |
| Silex, MO (Village) |
| Silo, OK (Town) |
| Siloam, GA (Town) |
