Carl Sandburg once wrote of Chicago, “They tell me you are wicked and I believe them,” but that wasn’t necessarily a dis. The storied poet and historian subsequently breaks down a laundry list of Windy City malfeasance, only to boldly proclaim, “Come and show me another city with lifted head singing so proud to be alive and coarse and strong and cunning.” It’s a perspective shared by the fiery young South Siders of Flatfoot 56, but the boys go one better than unyielding urban pride. On their second Flicker Records’ full-length Jungle of the Midwest Sea, a rollicking barrage of Celtic punk and hardcore roundhouses, a more universal message is clear: Where you live is who you are, so don’t blow it.

The ensuing 14-track onslaught more than underscores the sentiment. Comprised of brothers Tobin, Justin and Kyle Bawinkel (respectively frontman, drummer and bassist) along with tartan-toting multi-instrumentalist Josh Robieson, Flatfoot 56 attacks dark subject matter—avarice, faithlessness, cowardice—with a gravity that belies their barely legal ages. That said, in the tradition of their street-punk forefathers, they’re just as adept at dialing up bone-crunching good times. Most of the Flatfoot live show is improvised, and it’s all contingent on Robieson and crew making swift transitions between guitar, mandolin, bagpipes and whatever other eclectic instruments they bring to the party. “He’s got it down to a science,” Tobin says of Robieson’s equipment juggling. “We don’t really make set lists. We kind of go with hand signals because we like to play certain songs to get certain crowds involved. Because of that, Josh has become really quick at flipping instruments. He’ll have a guy stand on the side for bigger shows to throw him the instrument he needs. It helps to tailor our set to each crowd as opposed to playing the same songs every night.”

While Flatfoot is already accomplished entertainers—they’ll break out Twisted Sister or the Proclaimers for a broad audience, lesser-known Ramones scorchers for more discerning punk crowds—their principled intensity is unmatched. Jungle of the Midwest Sea’s title track is informed by Upton Sinclair’s infamous turn-of-the-century novel The Jungle, which single-handedly transformed Chitown via a scathing assault on the meat-packing industry and lower-class exploitation. (“I like it when bands write historical songs,” notes Tobin, who has a degree to teach high school history. “Iron Maiden was known for doing that a lot.”) Bouzouki-driven stomp “The Galley Slave” applauds courage in the face of adversity, and the breakneck “Loaded Gun” appeals for a progressive stance against the perpetuity of violence. The songs are rich in conscience, even deeper in metaphor.

Then there’s the grab bag of influences that color Flatfoot’s palette: Tobin fell for the Pogues after high school, ultimately incorporating elements of Oi!, hardcore, ska and even folk into his band’s populist mix. (“My dad always played things like ‘Do Your Ears Hang Low’ to us when we were kids, stupid little songs that basically mean nothing, but at the same time they’re funny little plays on words.”) And although it’s not their primary inspiration, Flatfoot’s love of old school Celtic traditional folk bands like the Dubliners and Chieftains is certainly among their most intriguing.

“When you look at the roots of Celtic music, most of that isn’t created by rich upper-class people—it’s a middle-of-the-lower-class style of music,” Tobin explains. “The best writers of some of the Celtic classics were all immigrants making nothing. It’s all about the rich oppressing them. Obviously, punk is not a very positive thinking genre as a whole either as it also comes from the lower-class kids.”

At the end of the day, Flatfoot covers a wide swath of the punk spectrum, from impassioned to idiosyncratic, and fans have their choice of which version to embrace. For what it’s worth, the band claims that the show’s in the audience, not onstage. That’s community. That’s reciprocation. That, says Tobin, is “what punk rock is all about.” “People come up to us all the time and say, ‘I busted my nose at your show,’ and we apologize and they’re like, ‘No, it’s the best breaking I’ve ever had,’” the frontman laughs. “It’s like a war wound. Not like we encourage that type of thing, but a lot of people take pride in remembering that show—they’ll have it the rest of their lives.”