The lineup for Riot Fest 2012 in Chicago, Ill. has been announced, and a slew of alternative and indie acts are lined up to play this year's edition of the gathering, which for the first time will be held outside instead of at indoor venues. Built to Spill, the Offspring, the Jesus and Mary Chain and the Gaslight Anthem are all on board for the 2012 Riot Fest, which runs from Sept. 14-16 at Chicago’s Humboldt Park.

Other bands scheduled to perform include the Promise Ring, the Screaming Females, Gogol Bordello, Japanther and the Reverend Horton Heat. More than 30 acts have already been confirmed, with more to be announced at a later date. Headliners include Rise Against, Iggy and the Stooges, Elvis Costello, a Day to Remember and Coheed and Cambria. Check out complete ticketing details here.

Past Riot festivals were held at indoor venues, but organizers made the move to the spacious outdoor location of Humboldt Park to prevent headlining sets from overlapping with each other, as they had in the past. “We were cannibalizing our own market a little bit,” explains founder and promoter Michael Petryshyn. “We decided to avoid that all together and put everything into one or two days.”

Meanwhile, organizers have expanded the brand by announcing the first-ever three-day version of the East Coast Riot Fest, which is set for July 19-21 at Festival Pier on Penn’s Landing in Philadelphia, Pa. Bands confirmed for that show include the Promise Ring, Refused, Off!, Boy Sets Fire and more, with additional acts to be announced shortly.

Want to win tickets to the Chicago Riot Fest? Head over to our sister site Loudwire to enter for a chance to win a pair of weekend passes (travel and accommodation not included).