GEORGE, WA - MAY 26: Marcus Mumford of Mumford & Sons performs as part of Day 3 of the Sasquatch! Music Festival at the Gorge
Tim Mosenfelder

Three years after playing a side stage at Sasquatch Fest in 2010, British folk outfit Mumford & Sons returned to the Gorge Amphitheater Sunday night to launch their U.S. summer tour as mainstage headliners, a No. 1 album under their belts. That's an aggressive curve on the Career Chart.

And even for Mumford & Sons, whose frontman Marcus Mumford gushes of romance and camaraderie in the band's rousing, arena-sized folk anthems, this was a very special gig. "If I die tomorrow and it was just the 25,000 of you and this music, I'd be happy," he said to the massive crowd. "If this were heaven, this would be the best place to be when you die."

True. But hopefully heaven will be a little warmer. Chilly temps and wind gusts had fans scrambling for jackets Sunday night, but didn't dampen their spirits too much. Mumford did a damn fine job of keeping those warm and toasty. He led the London band in fan favorites from Babel, their second album that topped the charts last year, selling 600,000 in its first week. It went on to nab the year's second best sales (behind Taylor Swift's Red, no less). 

"Who's ready to dance?" Mumford asked the crowd. "The Cave" and "Little Lion Man," both from the band's 2009 breakout album Sigh No More, certainly helped with that, as did a cover of Fleetwood Mac's "The Chain." "I Will Wait" and "Lover of the Light," meanwhile, delivered rock drama not via U2-style electric guitar riffs, but folk's rudimentary tools—acoustic guitar, banjo, mandolin, piano et al. It's super-sized folk and their version of the time-honored genre has met super-sized results: hit albums and singles, sell-out tours and headlining gigs at festivals. Though Mumford is still adjusting to the latter.

"We haven't headlined that many festivals—this summer it's changed, and that's f-cking terrifying," Mumford told the crowd. "It's your fault, and we're really grateful for it."

So are we.