On Feb. 21 the Orpheum Theater filled with Irish flat caps and Boston Bruins jerseys as Dropkick Murphys fans and Celtic punk rock enthusiasts ranging from ages 13 to 60 came to revel in Irish-American culture and timeless rock music. These were people who sported sleeve tattoos, clover leafs and Pabst Blue Ribbon tall boys, and they were ready to rock.

Established in 1996 in Quincy, Mass., the Murphys have changed members and record labels numerous times, but they’ve never changed their unique sound. The band cites AC/DC and the Ramones as its musical influences. More than 18 years of music has led the Murphys to opening for Aerosmith, touring with Bruce Springsteen, championing worker’s rights worldwide as well as in Madison and building a cult following that embraces the Murphys as a culture unto themselves. Additionally the Murphys’ songs have been featured in Academy Award-winning films such as Martin Scorsese’s “The Departed” and David O. Russell’s “The Fighter.”

Standing outside the venue, it became apparent how diverse the crowd was in terms of age. A middle-aged man told me he had to leave by 11 p.m. because he’s 40, married and has three kids. He stood next to a brute of a 20-something rocking a motorcycle crew vest and tattoos from head to toe. If you’ve ever seen “Sons of Anarchy,” you can imagine the make-up of the crowd.

Around 8:30 p.m., Memphis-based country/punk rock opener Lucero stepped onstage and delivered a mixture of soul, southern rock and country that absolutely killed. Imagine a cross between Creedance Clearwater Revival, Nirvana and Johnny Cash. If Lucero had played all night, everyone in the venue could have left content that the ticket money would have been well-spent.

Somewhere between the time Lucero hopped off stage and more PBRs were purchased, the lights went out and the excitement of the room built. Everyone rushed toward the front of the stage. Chants of “Let’s go Murphys” resounded throughout the ornate Beaux-Arts architecture of the Orpheum. The Dropkick Murphys took the stage and with the first hint of the first note being played, beers (amid other more unspeakable things) flew in the air. Going home without beer in your hair was out of the question.

For the next two hours, the Murphys played every track from new album Signed and Sealed in Blood along with older hits such as “Rose Tattoo.” Meanwhile the mosh pit was antagonized by a 60-year-old woman and the same 40-year-old man who had to be back by 11 p.m. Despite the “rough around the edges” look of the crowd, manners, civility and friendship encompassed every encounter and nothing was allowed to get out of control.

The show culminated with 60 or so fans on stage screaming the lyrics to the platinum hit “Shipping Up to Boston” along with the band. It was truly a transcendental moment. As everyone filed out, Frank Sinatra’s “My Way” played over the speakers and if only for a moment the crowd enjoyed the company and mellow banter around them. As if it needed to be said, the Dropkick Murphys put on a kick-ass show.