On October 14, 2014, Seattle Sounders FC announced the creation of a development team named Seattle Sounders FC 2, to join the USL PRO in 2015, while also unveiling the team logo. The concept behind the logo was that players in the development squad would "earn the crest" when they progressed on to the MLS first team.
| Current clubs:|
Arizona United | Bethlehem Steel | Charleston Battery | Charlotte Independence | Colorado Springs Switchbacks | FC Cincinnati | FC Montréal | Harrisburg City Islanders | Los Angeles Galaxy II | Louisville City | Oklahoma City Energy | Orange County Blues | Orlando City B | Pittsburgh Riverhounds | Portland Timbers 2 | Real Monarchs | Richmond Kickers | Rochester Rhinos | Rio Grande Valley FC Toros | Sacramento Republic | San Antonio FC | Seattle Sounders FC 2 | St. Louis FC | Swope Park Rangers | Toronto FC II | Tulsa Roughnecks FC | Whitecaps FC 2 | Wilmington Hammerheads
Clubs on hiatus: