(FORTUNE Small Business) – Time was you could glance down Main Street and identify which business was which simply by the symbol outside the shop. The local pharmacist would have a mortar and pestle; the tobacconist, a wooden Indian. Today, only one of those trade symbols is still widely used: the barber pole, whose enduring presence is largely due to the William Marvy Co., America's last barber pole manufacturer.

William Marvy didn't invent the barber pole (its red and white stripes date back to 11th-century Europe, when barbers were also surgeons and would hang their bloody bandages out to dry; the blue stripe was a 1900s nod to American patriotism), but he had the last word on it. He got his start selling barber supplies in the 1920s but was frustrated after working for two companies that went belly-up. So in 1936 he launched his own firm in St. Paul and took to the road, selling barber sundries--including poles--throughout southern Minnesota. Despite being a salesman, Marvy had long been fascinated with manufacturing, and after World War II he became convinced that he could build a better barber pole than the ones he was selling.

By 1950 he'd perfected his version. With its Lucite outer cylinder, cast-aluminum housing, and stainless-steel fittings, the Marvy pole was lighter, sturdier, and more durable than the others on the market. Hailed by the Wall Street Journal as the "first real improvement in the barber pole in a quarter century," it was an instant hit, and Marvy soon gave up his sales routes and set up a manufacturing plant. The four other pole companies then in business began losing sales to him, and by the late 1960s Marvy had cornered the market so thoroughly that his two remaining competitors were jobbing out their pole production to him. Marvy had the business all to himself not long after. Today it's safe to say that any barber pole currently operating in America is either a Marvy product or has been serviced with Marvy parts.

William Marvy died in 1993 (he remains the only nonbarber ever enshrined in the Barber Hall of Fame), but his company still operates in St. Paul. The $3 million firm is run today by his son, Bob Marvy, who reports that pole sales are down from an annual high of 5,100 in 1967 to only about 600 these days. That is partly because Marvy poles are simply made too well for their own good (Bob Marvy matter-of-factly says they should last "indefinitely"), but the biggest culprit turns out to be that all-purpose cultural scapegoat, rock & roll. "When the Beatles came to America, that was the turning point," says Bob. "Nobody wanted a tapered haircut anymore." The rise of hairstylists' shops, which don't often use barber poles, didn't help either.

The company has survived by diversifying, selling various beauty and grooming supplies. But while the poles now account for only about a quarter of the firm's business, they remain Marvy's signature product, and the company maintains meticulous records showing where each of its 77,000-plus poles was installed (including No. 75,000, which is in the Smithsonian's permanent collection). With two of Bob's sons already involved in the family business, the company is poised to maintain its Main Street pole position. "As long as people need a haircut," Bob says, "there will always be a market for what we do."