In 2013, they still refer to themselves as "That Little Ol' Band From Texas." But after Tres Hombres, there was nothing "little" about ZZ Top. The group (Billy Gibbons, Dusty Hill, Frank Beard) had already released two albums by this point (ZZ Top's First Album and Rio Grande Mud), and while we now recognize some of the songs as classics�"Goin' Down To Mexico," "Just Got Back From Baby's" and "Just Got Paid," for instance�they weren't hits at the time. Tres Hombres, though, changed the game. Released 40 years ago this month, it contained "Waitin' For The Bus/Jesus Just Left Chicago" and a pair of anthems that still can rock a party, decades later: "Beer Drinkers And Hell Raisers" and "La Grange." Suddenly, ZZ Top was no longer just a Texas band, it was a celebrated American institution.

Singer/guitarist Billy Gibbons tells Radio.com that Tres Hombres brought the trio to the so-called next level, although they only noticed gradual differences due to their hectic life on the road. "Let's just say it was a big door opener for us," he says. "The band entered the nonstop, continual touring mode before Tres Hombres hit, then we noticed the venues were getting bigger and the road map was getting longer, both nationwide to worldwide."

In an era when lots of bands were getting more "progressive," the members of ZZ stuck to their working class blooze-rock roots. Not every rock fan may have followed the lyrics of, say, Pink Floyd, Led Zeppelin and Yes. But in "Beer Drinkers And Hell Raisers"�when Gibbons sang "I'll be here around supper time" and bassist Hill answered "With my can of dinner and a bunch of fine!"�you can bet that plenty of fans from Texas to North Dakota to California knew what they were talking about and were singing (and partaking) right along with them.

"[That was] ZZ's continual sound of the endless party," Gibbons says of the dual lead vocals. "Lots of people, lots of fun, maybe some mayhem. Sin, sand, suds, and a second line dual singer's salvation to bring the message across."

Speaking of "sand" and "sin," another song on Tres Hombres turned its attention to the world's oldest profession. "La Grange" celebrated a particular Texas bordello known as "The Chicken Ranch," and it became the band's biggest hit yet�not to mention one of its most enduring.

Did the bandmembers, though, know "La Grange" would be a hit when they recorded it?