|Founder||Francisco Marcos |
|United Soccer League divisions|
|Championship||League One||League Two|
United Soccer League (USL), formerly known as United Soccer Leagues, is the organizer of several soccer leagues with teams in the United States and Canada. It includes men's and women's leagues, both professional and amateur. Leagues currently organized are the USL Championship, USL League One, USL League Two and the youth Super Y-League. It is directly affiliated with the United States Soccer Federation, the United States Adult Soccer Association and the Canadian Soccer Association. The USL is headquartered in Tampa. 
This section is in a list format that may be better presented using prose. (December 2018)
- 1986 Established as Southwest Indoor Soccer League
- 1989 Added an outdoor league known as the Southwest Outdoor Soccer League. This was soon changed to Southwest Independent Soccer League which included both the indoor and outdoor leagues.
- 1990 Renamed Sunbelt Independent Soccer League
- 1991 Renamed United States Interregional Soccer League
- 1995 Renamed United States International Soccer League
- 1995 Renamed United Systems of Independent Soccer Leagues and formally established professional Pro League and amateur Amateur Premier League
- 1995 The USL W-League women's semi-pro league is launched.
- 1996 Established Select League consisting of strongest teams from Division 3 Pro League and Amateur Premier League in hopes of gaining Division 2 sanctioning.
- 1997 Select League and the former American Professional Soccer League merged to form A-League under the USISL umbrella.
- 1999 Umbrella USISL changed its name to the modern United Soccer Leagues.
- 2009 Nike sells organization to NuRock Soccer Holdings, LLC. As a result, nine clubs left the First Division to form the North American Soccer League: Atlanta Silverbacks, Carolina RailHawks FC, Miami FC, Minnesota Thunder, Montreal Impact, Rochester Rhinos, Tampa Bay Rowdies, Vancouver Whitecaps, and the AC St. Louis expansion group.   United Soccer League was a division in the temporary USSF Division 2 league. 
- 2010 USL announced the formation of USL Pro, which merged the USL First Division and USL Second Division. 
- 2011 Inaugural season of USL Pro.
- 2011 USL takes over operation of the Major Indoor Soccer League.
- 2013 USL Pro and Major League Soccer announce a multi-year agreement, beginning that season, to integrate MLS Reserve League play with USL Pro teams, first through team affiliations and "interleague" play, eventually fully merging MLS Reserves into the USL Pro structure.
- 2013 The W-20 League is launched, a youth league that is operationally aligned with the USL W-League. 
- 2015 USL Pro renamed United Soccer League
- 2015 USL W-League and W-20 League cease operations. 
- 2017 USL is granted Provisional Division II status by U.S. Soccer. 
- 2017 USL creates USL Division III league and files for Division III status with U.S. Soccer.
- 2018 USL announces re-branding of its top league to the USL Championship, USL Division III to USL League One, and the Premier Development League to USL League Two beginning with the 2019 season
Founded in 1985 by Francisco Marcos, the Southwest Indoor Soccer League was first intended as a minor indoor league associated with Major Indoor Soccer League.  The league began with five teams, all owned by individuals who owned or operated indoor soccer arenas in the Southwest United States. League headquarters was in Austin, Texas. In 1986, Marcos' team, the Austin Sockadillos, entered the league giving it six teams. By 1989, the league had set its sights on greater prospects than remaining a small, semi-professional indoor league. A 1989 press release stated, "It is envisioned the league will be part of the USSF's plan to professionalize soccer in the USA prior to the 1994 World Cup, and the league plans to push its teams to be considered for the "three-tiered first, second and third divisions" plan the USSF envisions for soccer." 
The USL began operations in 1986 as the Southwest Indoor Soccer League, a semi-professional indoor league. The league quickly expanded and added an outdoor season in 1989. In 1991, the league renamed itself the United States Interregional Soccer League. By then, the outdoor league overshadowed the indoor league which continued to slowly dwindle in importance. By the 1997–98 season, only five teams remained indoors while the outdoor season had over a hundred teams divided into a three-division structure. This led the league to stop running an indoor league.
In 2010, the USL began to consider relaunching an indoor season. However, it decided instead to take over operations of the Major Indoor Soccer League; beginning indoor operations in 2011. The champions were determined by a single games in 1987, 1988, 1992, 1993, 1994, 1995, 1996 and 1998. The champions were determined by a best of three series in 1998 and a best of five series in 1989, 1990 and 1991 and a home-and-home series in 2012 and 2013.
|1986/87||Addison Arrows||7–2||Lubbock Lazers|
|1987/88||Oklahoma City Warriors||3–0||Austin Sockadillos|
|1988/89||Lubbock Lazers||3 games to 2||Austin Sockadillos|
|1989/90||Addison Arrows||3 games to 0||Phoenix Hearts|
|1990/91||Colorado Comets||3 games to 0||Oklahoma City Warriors|
|1991/92||Oklahoma City Warriors||7–2||Atlanta Magic|
|1992/93||Atlanta Magic||11–7||Arizona Cotton|
|1993/94||Atlanta Magic||8–3||Chattanooga Express|
|1994/95||Atlanta Magic||6–3||Oklahoma City Slickers|
|1995/96||Baltimore Bays||10–8||Atlanta Magic|
|1996/97||Baltimore Bays||5–4; 13–10||Tulsa Roughnecks|
|1997/98||Baltimore Bays||11–4||Tulsa Roughnecks|
|The USISL ceased operating its own indoor league in 1998.|
From 2011–2014, the USL operated the MISL.
|2011/12||Milwaukee Wave||14–2; 12–10||Baltimore Blast|
|2012/13||Baltimore Blast||21–12; 8–6||Missouri Comets|
|2013/14||Missouri Comets||15–8; 4–19; 6–4||Baltimore Blast|
In 1989, the Southwest Indoor Soccer League added a summer, outdoor season known as the Southwest Outdoor Soccer League. In 1990, the league dropped both "indoor" and "outdoor" from its name as it ran both a semi-professional indoor and outdoor season. By 1995, the outdoor season had grown to such a size that the USISL, as it was known at the time, split the league into two levels, the aptly named, fully professional Professional League and the semi-professional Premier League. In 1996, the USISL added a third, higher, Select League. This was formed from the strongest teams from both the Professional and Premier League. The Select League, along with the competing A-League, both received official Division II status from FIFA. However, the A-League was in decline while the USISL was expanding. Therefore, in 1997, the A-League ceased operations and merged into the USISL Select League which was renamed the USISL A-League. From that point, the USL's three-level structure remained stable until 2010. Some teams left to start the North American Soccer League and the First and Second Divisions were merged to become the USL Professional Division.
|USL Championship (Division II)||USL League One (Division III)||USL League Two (Semi-Pro)|
|Season||Winner||Final score||Runner-up||Season||Winner||Final score||Runner-up||Season||Winner||Final score||Runner-up|
- Kennedy, Paul (March 7, 2018). "Francisco Marcos: 'The impatient train left a long time ago'". Soccer America. Retrieved December 14, 2018.
- "About". www.uslsoccer.com. Retrieved August 22, 2017.
- "USL outcasts set to launch new league in 2010". Soccerbyives.net. November 10, 2009. Retrieved October 8, 2011.
- Molinaro, John F. (November 10, 2009). "CBC Sports: Whitecaps, Impact to form breakaway league". Cbc.ca. Retrieved October 8, 2011.
- "US Soccer Federation To Oversee Combined NASL/USL League". Goal.com. January 7, 2010. Retrieved January 8, 2010.
- "USL Restructures Professional Division". www.uslsoccer.com. September 8, 2010. Archived from the original on October 11, 2010. Retrieved September 10, 2010.
- "W-20 League Set for 2013 Debut". www.uslsoccer.com. April 4, 2013. Archived from the original on April 9, 2013. Retrieved June 29, 2013.
- "W-League Statement". United Soccer Leagues (USL). November 7, 2015. Archived from the original on November 19, 2015. Retrieved November 7, 2015.
- "U.S. Soccer Board of Directors Grants Provisional Division II Status to NASL and USL". U.S. Soccer. January 6, 2017. Retrieved July 24, 2017.
- "Indoor Soccer Comes to City Warriors Feature "Cream of Crop' Players". December 22, 1986. Retrieved August 22, 2017.
- "earlyyears". www.unm.edu. Retrieved August 22, 2017.