Major League Soccer (MLS) is a professional soccer league based in the United States and sanctioned by United States Soccer Federation (U.S. Soccer). The league comprises 16 teams, 15 in the U.S. and one in Canada, which is scheduled to become 18 teams by the beginning of the 2011 season. MLS represents the top tier of the American and Canadian soccer pyramids.
Major League Soccer was founded in 1993 as part of the United States' bid to host the 1994 FIFA World Cup. The first season took place in 1996 beginning with 10 teams. Seasons run from late March or early April to November, with teams playing 30 regular season games each. Eight teams compete in the postseason MLS Cup Playoffs culminating in the championship game, MLS Cup.
The 2009 Major League Soccer season runs from March 19 through November 22. The 15 teams in the league are divided into the Eastern and Western Conferences — seven in the Eastern Conference, eight in the Western Conference. Each team plays 30 games, evenly divided between home and away matches. Each team competes against every other team twice, home and away, for a total of 28 games. The remaining two games are intra-conference matches, often highlighting geographic and conference rivalries. The team with the most total points at the end of the regular season is awarded the Supporters' Shield. Eight teams then proceed to the MLS Cup Playoffs ending in the single match MLS Cup final.
MLS has three automatic berths in the CONCACAF Champions League with extra berths possible via the U.S. Open Cup and the Canadian Championship. For CONCACAF Champions League 2009–10, qualifying teams include MLS Cup 2008 and Supporters' Shield winner the Columbus Crew, Supporters' Shield runner-up the Houston Dynamo, MLS Cup runner-up the New York Red Bulls, 2008 U.S. Open Cup winner D.C. United, and 2009 Canadian Championship winner Toronto FC. Columbus and Houston are automatically seeded into the Group Stage. New York, Toronto, and D.C. are required to play in the Preliminary Round.
MLS also has four berths in SuperLiga, a competition jointly organized by MLS and Mexico's national football governing body, the FMF. The top four overall teams from the 2008 season, excluding those participating in the Champions League, qualify for SuperLiga 2009. This includes the Chicago Fire, the New England Revolution, the Kansas City Wizards, and Chivas USA.