They’re staples on rock radio. They’re “B-b-b-bad.” They’re from Delaware. And they’ve been rocking stages across the country and around the world for 40 years. George Thorogood and the Delaware Destroyers live out their rock n’ roll destinies onstage night after night and show no signs of letting up anytime soon.

It hasn’t always been like this, and Thorogood started out sounding quite a bit different from what he does now. He’s always been interested in the blues and early rock n’ roll. But while his trademarked sound is now a ferocious electrified slide guitar, he started out on the other end of the spectrum, playing acoustic country-style blues in the vein of Robert Johnson.

That may come as a surprise to fans of his accustomed to his sound on hits like “Haircut” or his cover of John Lee Hooker’s “One Bourbon, One Scotch, and One Beer.” But soon after he got his start, he decided to change things up and start an electrified band with some high school friends in tow, dubbing themselves the Delaware Destroyers (they were from Wilmington).

This was in the early 70s. It took them several years to land a recording contract with independent Rounder Records. They did record a demo in 1974 called Better than the Rest, but it wasn’t released until after they had their first taste of success. That came with the one-two punch of George Thorogood and the Destroyers (1977) and Move It on Over (1978). The latter was named after a well-received cover of the Hank Williams song, which has gone on to become familiar to rock radio listeners everywhere.

The following year, the band released a rousing rendition of the Bo Diddley tune “Who Do You Love,” and soon they found themselves warming up for the Rolling Stones on their 1981 tour as well as playing on Saturday Night Live. All of that, combined with a move from Rounder to major-label EMI, set the stage for the blockbuster success of their next album, Bad to the Bone (1982).

Chances are you’ve heard the title cut many times over. It’s become inescapable, and not just on rock radio, but in movies and on television shows, advertisements, sports stadiums – just about anywhere music is heard. That kicked off something of a golden era for the Destroyers in the 1980s, where albums like Maverick and Born to Be Bad went Gold, and the band toured constantly and developed a dedicated fan base. Their touring moxy is perhaps best typified by their “50/50” tour in 1981, during which the band played 50 shows in 50 states in the course of 50 days – 1 state per day.

As simple as Thorogood’s music is on the surface, at least insofar as its directness, it can be difficult to pin down how exactly to define his sound. Part blues, part rock, with a little bit of country and R&B mixed in for good measure, it’s a little difficult to put a tag on it with anything other than “boogie-blues-rock.”

Though Thorogood insists his band plays rock n’ roll, the band is clearly blues-based, and they have a bluesman’s penchant for valuing delivery over originality. In other words, it doesn’t matter so much who wrote the song, whether it was you or someone else; it’s how you deliver it. That’s why playing covers and traditional music is such a deeply entrenched aspect of blues artists’ repertoires. But, to Thorogood, he’s just playing good old rock n’ roll.

“I’m probably into more of a traditional rock-blues-boogie thing in the vein of ZZ Top, Steppenwolf, that kind of thing,” he says. “We’re a lot closer to the rock world than to the blues world.

“People say ‘Well your roots are in blues,’ but everybody’s roots are in blues. It’s how everybody starts. That’s what you start playing first and you move along from there.”

Throughout their early period and even going into the present day, Thorogood and the Destroyers have never strayed much from their signature sound – simple, raw, direct, blazing blues-rock. After the appearance of 1993’s Haircut and its hit title track, the band’s record sales went into decline, although their audience for live shows never abated.

Whether the band was playing for big crowds or small, though, the Destroyers always did their best to put on a high energy show. That’s a lesson Thorogood learned in the 70s from the great Chicago bluesman Hound Dog Taylor, whom the young guitarist opened for on a number of occasions.

“He taught me – him and John Hammond were the two most influential people I ever saw as far as work ethic,” says Thorogood. “Those two acts, they were always powerful every time I saw them. There could be 15 people in the place or 1,500 – didn’t make any difference. So, you know, I paid close attention to those incredible entertainers”

And, just as in the great tradition of the blues, the band’s delivery is more important than who wrote the words. Covers have always been a big part of the Destroyer’s recorded catalog, and recent albums have continued this trend, consisting mainly of covers with a few originals thrown in for good measure.

But that hardly matters when you turn in records as scorching as 2009’s The Hard Stuff and 2011’s 2120 South Michigan Avenue, a tribute to the great Chicago blues label Chess Records. After all, when asked whether he prefers writing and recording or playing live, Thorogood answers by simply asking, “What do you like better, sending out invitations to a party, or going to a party?”