Prada, Armani, Hugo Boss, Calvin Klein, Rockmount.

Um, Rockmount?

Whether you’re aware of this iconic fashion brand or not, you’ve seen it many times. Paul McCartney, when he hosted Saturday Night Live, wore not one, but two different Rockmount shirts. Heather Ledger and Jake Gyllenhaal (and indeed most of the entire cast) donned Rockmount’s snap-button shirts in Ang Lee’s Oscar-winning Brokeback Mountain. In fact, the shirts worn by Ennis Del Mar and Jack Twist were bought in a charity auction for $101,000 and now reside, entwined together for eternity, in L.A.’s National Autry Center, a museum devoted to Gene Autrey and all things western.

Ronald Reagan, Elvis, Miley Cyrus, Robert Redford, Matthew McConaughey, Tom Hanks and just about every honoree in the Rock and Roll Hall of Fame wear or have worn (sorry Elvis) the shirts that Papa Jack Weil started making back in 1946. He served as CEO of the company and showed up every day, sitting at a wooden desk near the entrance of the five-story red brick warehouse in Denver’s Lower Downtown (LoDo), until he died in 2008 at 107. He said he owed his longevity to the wisdom of quitting smoking at 60, giving up drinking at 90 (except, of course, for twice-weekly medicinal shot of Jack Daniels) and losing the red meat at 100.

He told his grandson, Steven Weil, who now runs the store and the Rockmount brand (It’s short for Rocky Mountains, in case you’re wondering) that he got up every morning, read the obits and if his name wasn’t in there, he’d get dressed and go to work.

Papa Jack more or less invented the Western shirt. Or at least the first with snaps. Still in production today, these slim-fitting shirts (Papa Jack claimed they were less likely to get snagged on cactus or sagebrush) with the signature sawtooth pockets, yoke and shotgun cuffs are so much a part of the aura of the West that samples reside in the permanent collection at the Smithsonian.

At the historic store in LoDo (1626 Wazee) where the company has been making shirts for 65 years, there’s a small upstairs museum with saddles, quilts, cowboy lunchboxes, photographs, three generations of shirts and a couple “Jack A. Weil Boulevard” street signs from the city’s annual acknowledgement of the founder’s birthday.

Still scratching your head about Rockmount? Here are a couple other places you may have seen the iconic shirt:

** William Shatner wore one on an episode of “Boston Legal.”

** Costume designers for the 1993 Nicolas Cage flick “Red Rock West” purchased 20 of the same white shirt to ensure Cage’s character was always emanating pristine Rockmount.

** Robert Redford outfits the entire staff at his Sundance Resorts in custom-made Rockmounts.

** Clark Gable wore one in “The Misfits” with Marilyn Monroe

** Rockmount once sent a shipment to Antarctica

** When Cream performed their reunion concert in 2005, Eric Clapton sent an email the day before requesting a couple dozen shirts. Steve, who had to tell him there was no way even Federal Express could get them there on time, ended up flying over and hand-delivering them to London’s Royal Albert Hall.

Why does rock-‘n’-roll love Rockmount so much?

“Beats me,” Weil said. “Luck, I guess. And people seem to like the story. We don’t change with the wind. Rockmount is about classic American design.”