High Quality Content by WIKIPEDIA articles! Seattle Sounders FC is an American professional soccer club based in Seattle, Washington. The club competes in Major League Soccer (MLS), the top professional soccer league in the United States and Canada. Sounders FC was established in November 2007 as a MLS expansion team, making it the 15th team in the league. Fans chose the Sounders name through an online poll in 2008, making the Seattle Sounders FC the third Seattle soccer team to share the moniker.