Seattle was finally awarded a MLS franchise in 2007 . The bid was helped by Allen 's ownership of the 60,000 capacity Qwest Field , home ground to the NFL 's Seahawks -- an arena built with intention of hosting an MLS team . The Sounders debuted in the MLS in 2007 , winning MLS Cup . The Seattle franchise also reached the MLS semifinals . The Sounders play at Los Angeles Galaxy , and had an average attendance of 30,897 .
Seattle was finally awarded a MLS franchise in 2007 . The Sounders debuted in the MLS in 2007 , winning MLS Cup . The Seattle franchise also reached the MLS semifinals . The Sounders play at Los Angeles Galaxy , and had an average attendance of 30,897 .