Salmonstock music festival features scores of bands and educational booths. Last weekend, volunteers passed out informational flyers and anti-Pebble mine stickers. Fire-breathing salmon flanked the main stage. Face-painted kids sprinted up an inflatable slide and hundreds packed into beer gardens with their Salmonstock-issued reusable pint glasses.

Becca Wolfe, 21, was a volunteer at the festival, working four-hour shifts in exchange for free entry.

"I'm here for various reasons," Wolfe said. "I'm here -- for the official reason -- because I oppose Pebble mine, and we were also saying last night, I'm here because it's the biggest party in Alaska."

Read more: Peace, music and politics at Salmonstock, 'the biggest party in Alaska'