Mike Petryshyn, co-founder of Riot Fest, described the dozen-year plus growth of his annual rock and roll carnival as organic.

“There was no plan of ‘10 years from now we’re going to be outside,’ when we started,” he said. “That wasn’t even a thought. It was ‘Let’s do this and see what happens.' ”

Running Friday through Sunday at Chicago’s Douglas Park, Riot fest has now been an annual Chicagoland music staple for 13 years.

Its inaugural run in 2005 was confined to two days and one venue at the now-defunct Congress Theatre. The lineup was a mix of national and local-based punk-minded acts ranging from icons such as the Dead Kennedys and The Angry Samoans to then-upstarts such as Store Bought Rebels and Out of Place.

The festival grew slowly but steadily over the years, extending to three days and to Chicago venues such as Metro, Subterranean and Congress Theater as well as expanding outside of Chicago to Denver, Toronto and Dallas. The festival came to the great outdoors in the Windy City for the first time in 2012.

Along with location and venue growth, Riot Fest has seen its roster profile rise to include higher profile artists and bands. Past headliners have included punk icons Iggy and the Stooges, alternative trailblazers The Replacements and The Cure and more recent trailblazers such as Sleater-Kinney, Death Cab for Cutie and Weezer.

Nearly 100 acts are scheduled for this year’s festival, with Nine Inch Nails headlining Friday, Queens of the Stone Age headlining Saturday and just-reunited emo punks Jawbreaker concluding the musical festivities Sunday.

Other acts of note on this year’s Riot Fest lineup include New Order, Wu-Tang Clan, Prophets of Rage, M.I.A., Ministry and At The Drive In.

“The focus is relatively the same (compared to previous years),” Petryshyn said of their musical lineup. “There’s (acts) that we’ve been working on (bringing to the festival) for years that have come through, but we’re not taking a different path in terms of style.”

This year’s fest, sadly, marks the first Riot Fest without co-founder Sean McKeough, who passed away last fall due to complications from throat cancer.

Petryshyn said McKeough’s “work ethic, his passion about Riot Fest and his enthusiasm for it” is sorely missed.

“He really took a lot of pride in building the festival,” Petryshyn said. “It just didn’t happen overnight. It took a full year of developing and planning and he really excelled at that. And having him around as a confidant, that’s irreplaceable.”