DETROIT LAKES, MINN. -

Ever the affable musician, Mason Jennings went so far as to apologize for the fact that Thursday night was his first time at the 10,000 Lakes Festival.

"I live in Minneapolis, and I can't believe it's taken me this long," he told the crowd as the sun set over the trees and lakes within view from the stage.

Jennings was not alone among Twin Citians making their inaugural four-hour pilgrimage to the 10KLF. Now in its seventh year, the tie-dyed rock 'n' roll answer to the wildly successful big-hat country music marathon We Fest, 10,000 Lakes has slowly built a national reputation even while turning to a wider array of Minnesota acts for star power this year.

Two other big names from the metro area music scene, Atmosphere and Cloud Cult, also played the festival for the first time Thursday and Friday. By tonight, when the four-day camp-out culminates with its biggest headliner to date, the Dave Matthews Band, the crowd is expected to swell to around 20,000, including lots of newbies from the Cities driving up just for the night.

Laura and Joe Emiola of Rosemount were among the 10,000 fans already there Thursday. The couple came to their first 10KLF to celebrate their second wedding anniversary.

"We're finally using the tent we got for a wedding present," said Laura, 25, who said they made the trip mostly for Thursday's headliner, Wilco.

Jeff Tweedy, frontman for the Chicago sextet, proved he was also a 10KLF virgin when he playfully urged the crowd to throw glow sticks -- the psychedelic party accessory of choice -- at the band. About a thousand glow sticks later, a dozen or so of which grazed his head, Tweedy said, "I have to admit, I fully underestimated the amount you had."

Anybody who underestimated Wilco's appeal to 10KLF's core audience -- jam-band fans -- clearly hasn't seen its live show of late.

The band -- which has announced an Oct. 2 date at Roy Wilkins Auditorium in St. Paul (on sale Aug. 1) -- won over the baked-over crowd with its recent topsy-turvy concert staples, songs with buckshot-like guitar parts such as "Spiders (Kidsmoke)" and "Impossible Germany." The new "Bull Black Nova" was also loaded with shredability, but other songs from the group's month-old album harked back to the more melodic, classic charm of early Wilco albums, including "Sonny Feeling," "One Wing" and "Country Disappeared."

Thursday's fest was also a good test for the mass appeal of Atmosphere, who performed right after Wilco on the second stage. The Minneapolis hip-hop stalwarts showed they know how to play to rock crowds, delivering extra-heavy versions of "Puppets" and "Shoulda Known" before a thunderstorm cut their set short after an hour.

Fans might have suffered musical whiplash walking from Atmosphere's set to the Barn Stage (outside an actual barn), where Ernest Tubb-voiced country music guitar-wiz Junior Brown delivered lightning on his two-neck "guit-steel" instrument before also being cut short by the weather. Other prestorm highlights Thursday included the Honeydogs, whose new opus "Good Fight" would have fit in perfectly during Wilco, and the Ohio band Mifune, who blended Afrobeat and psychedelic rock.

The festival's more Minnesotan lineup didn't turn off 10KLF regulars from around the country, including Danny Ames, 29, of Chicago, a rock fest veteran who came for the fifth year in a row.

"It's one of the best festivals in the country for camping," Ames said. "It's still small enough where the campgrounds aren't overrun, but big enough to put a really great lineup together."

See Wilco's set list at startribune.com/poplife

chrisr@startribune.com • 612-673-4658