In 2019, the Timbers Army made national news as they clashed with the MLS front office over the use of the Iron Front symbol on flags flown by Timbers supporters. MLS banned the anti-fascist symbol along with far-right regalia in a blanket ban of “political signage”, which the Army contested, arguing in a statement that opposition to fascism, racism, and sexism was not political.[93] A protracted public battle between the Army and MLS brass occurred, culminating in a protest during the August game against Seattle where the TA deliberately stayed silent for the first 33 minutes of the nationally televised clash to commemorate 1933, the year that the Iron Front was disbanded in Nazi Germany.[94]

After the protests by the Timbers Army gained media exposure, Major League Soccer officials announced they would meet with the Army and other supporter groups around the league. A month later, on September 24, 2019, the league announced it would be reversing the policy that prohibited the Iron Front, allowing Timbers supporters to use the symbol again.[95] This was a rare instance in American sports (and one of the first in MLS) that a supporter group had directly taken on the league with an organized response and forced a change in policy.[96]

The Sounders FC Alliance was established at the request of minority owner Drew Carey, who was named its chairman.[244] Based on the fan association at FC Barcelona, members of the Alliance have the ability to vote on the removal of the general manager and on other team decisions. Season ticket holders become automatic members, while non-season ticket holders may buy into the Alliance for a fee. Membership benefits include voting privileges, an invitation to the annual meeting and other team perks. Members may also be elected to the Sounders FC Alliance Council by receiving at least 25 nominations from other members on an annual basis. The first vote on retaining or replacing Sounders general manager Adrian Hanauer was held in late 2012. After 13,775 votes registered, Hanauer was retained by the Alliance.[245]

Carey also requested that the Sounders have their own marching band, the first of its kind in MLS.[246] This led to the creation of Sound Wave, a 53-member marching band consisting of brass and marching percussion.[247] The band plays music from multiple genres, such as Latin, rock and pop,[247] and sits on the north end of Lumen Field.[248] The March to the Match, in which fans march from Occidental Park to Lumen Field before each home match, has been accompanied by Sound Wave.[249] The club’s fight song is “Salute to the Olympians” by Henry Mancini, which had been adopted by the NASL Sounders in 1974 and later used by the USL Sounders.[250][251]

Besides the Alliance, there are four recognized, independent supporters groups for the Sounders.[252] Emerald City Supporters (ECS), which formed in 2005 to support the USL Sounders, is the largest supporter group and sits in the south end of the stadium (nicknamed the “Brougham End”)[253] in sections 121–123.[254] The Eastside Supporters, established in 2010 to recognize fans from the Eastside region, are located in section 150.[252] Gorilla FC, an anti-fascist supporters group that fundraises for charitable causes in the Puget Sound region, is based in section 120.[255][256] The North End Faithful sit in the north end of the stadium.[257]