When the A-League became the USL First Division in 2005, the league comprised 12 teams: Atlanta Silverbacks, Charleston Battery, Minnesota Thunder, Montreal Impact, Portland Timbers, Puerto Rico Islanders, Richmond Kickers, Rochester Raging Rhinos, Seattle Sounders, Toronto Lynx, Vancouver Whitecaps, and Virginia Beach Mariners.

The Calgary Mustangs, Edmonton Aviators, and Syracuse Salty Dogs, all of whom competed in the final A-League season in 2004, folded during the offseason, and did not take up their places in the new league.

After lawsuits were filed and heated press statements exchanged, the United States Soccer Federation (USSF) declared they would sanction neither the NASL nor the USL First Division in 2010, and ordered both "camps" to work together on a plan to temporarily allow their teams to play a 2010 season.

Their spot in the league was taken by the Cleveland City Stars, who won the USL Second Division title in 2008, and voluntarily moved up to USL-1 for the 2009 season,[6] folded at the end of the year.

On December 2, 2009, Inside Minnesota Soccer reported that the USL had asked the City Stars to terminate the contracts of all the players, as the franchise was to be dissolved.

[7] On June 19, 2008, an announcement was made that an expansion slot had been awarded to a Tampa Bay, Florida-based franchise led by main investors Andrew Nestor (CEO) and Hinds Howard (chairman) of Citrus Ventures.

Prior to the 2009 NASL split several other cities had been mentioned as being locations where future USL-1 franchises might launch, including St. Louis, Missouri (led by the current USL Premier Development League (PDL) franchise St. Louis Lions);[9] Orlando, Florida (with Mexican side Pachuca being rumored as connected to it);[10] Milwaukee, Wisconsin; Detroit, Michigan; Hamilton, Ontario;[11] San Antonio, Texas; and Ottawa, Ontario.

[13] Unlike most other nations, there is no system of merit-based promotion and relegation in the American and Canadian pyramids, meaning that the champions of USL-1 could not move up to Major League Soccer and, similarly, the worst teams in MLS were not in danger of being demoted to USL-1.

The top seven teams advanced to the playoff tournament, with the Commissioner's Cup winner (regular season champion) receiving a bye into the semi-finals.