The United Soccer Leagues (USL) is directly affiliated with the United States Soccer Federation (USSF), United States Adult Soccer Association (USASA) and the Canadian Soccer Association (CSA). The USL is the parent organization for the men's lower division leagues of US Soccer USL First Division (second division), USL Second Division (third division), and Premier Development League (PDL) (fourth division). The top division for US men's soccer is Major League Soccer (MLS). The USL also includes a women's league W-League and the top flight youth league the Super Y-League .

The USL structure allows for the Second Division champion to be promoted to the First Division, provided that the team to be promoted meets criteria set by USL and the USSF, and space exists. A formal relegation process may also be added at a future date.

USL rosters may consist of a maximum of 26 players, with 18 desginated for each game. Each team is permitted a maximum of five (5) foreign players on its active game-day roster and a maximum of seven (7) foreign players on its master roster. In the PDL and W-League, at least three players in a full 26-player roster must be under 19, in accordance with guidelines set by the USASA and USSF. In the PDL, a maximum of eight (8) players may be over the age of 23.