Major League Soccer's other newcomers this year, the Vancouver Whitecaps, also date back to the NASL and took the league's championship back in 1979. The team brought in more than 29,000 per game during its height in 1983 and, like the Timbers, spent much of the past 26 years in the lower-division United Soccer League. This year, however, they already are bringing in more than 20,000 fans per game while playing at their temporary home in a Canadian Football League stadium. The Whitecaps are slated to move to soccer-specific BC Place later this year, but their current attendance is more than either the American League Central-leading Cleveland Indians or the AL East's last-place Baltimore Orioles have been able to manage.

A fan base that has your back even before you hit MLS doesn't hurt. A big, green reason for the Timbers' early success is the team's 3,600-member group of Timbers Army supporters, which have backed the team for nearly a decade and carry on Timbers traditions such as former mascot Timber Jim's chainsawing of a log each time the team scores a goal. The more than 530 members of the Vancouver Southsiders, meanwhile, have not only helped make the Whitecaps' home field sound like a European pitch, but been featured prominently in the team's marketing.

MLS' most popular teams usually come with boisterous booster groups, including the 5,200 members of the Sons of Ben who sit behind the goal in the "river end" of Philadelphia's PPL Park cheering the Union, the La Barra Brava and Screaming Eagles groups that crowd around midfield at RFK Stadium for DC United and the longest-serving group of supporters in MLS, the Empire Supporters Club.

"The supporters groups for Major League Soccer clubs are the lifeblood of the experience in the stadium," Courtemanche says. "The clubs with the larger supporters groups are leading the league in attendance."

That's certainly the case in Seattle, where the Sounders are bringing in a league-leading 37,000 per game while playing in the reduced-capacity CenturyLink ( CTL) Field, which normally hosts the NFL's Seattle Seahawks. They get 2,000 fans a night just from their Emerald City Supporters group, with firms such as Gorilla FC adding to the Sounders' loud and lively base. They're the only team in MLS with a marching band, the Sound Wave, and that group leads a march through the city to the stadium before every home game.

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