| Sacramento Gold FC | — | 2009 | — |
| Sacramento Knights | — | 2003 | Folsom High School |
| Salinas Valley Samba | — | 2004 | Watsonville High School |
| San Diego Boca F.C. | — | 2009 | Balboa Stadium |
| San Diego Flash | San Diego | 1998 | Mira Mesa Senior High School |
| San Diego Pumitas | — | 1999 | Balboa Stadium |
| San Diego United | — | 2008 | Torero Stadium |
| San Francisco Stompers FC | Hayward | 2012 | Pioneer Stadium |
| Santa Ana Winds FC | Santa Ana | 2009 | Santa Ana Stadium |
| Santa Cruz County Breakers | Santa Cruz | 2007 | — |
| Saturn FC | — | 2009 | — |
| Seacoast United Mariners | — | 2011 | Fitzpatrick Stadium |
| Seacoast United Phantoms | Portsmouth | 2010 | Portsmouth High School |
| Shreveport Rafters FC | Shreveport | 2016 | Independence Stadium |
| Sioux Falls Thunder FC | — | 2016 | — |
| Sonoma County Sol | Santa Rosa | 2004 | Casa Grande High School |
| Southern California Fusion | Carlsbad | 2004 | — |
| Sporting Arizona | Arizona | 1989 | — |
| TSC Maryland Red Devils | — | 2009 | — |
| Tucson Tiburons | Arizona | 2003 | Mountain View High School |
| Utah Salt Ratz | Salt Lake City | 2003 | Rice–Eccles Stadium |
| West Texas FC | Midland | 2008 | Astound Broadband Stadium |
| Zanesville Athletic FC | — | 2012 | — |