Ask any Dublin Dr Pepper bootlegger what the fuss is all about. They'll tell you that the top-shelf, premier cru of Texas soda pop is selling for eight bucks a six-pack in some stores — when you can find it.

Back in the 1970s, when soft drink bottlers across the country began sweetening their sodas with high-fructose corn syrup, the oldest Dr Pepper bottling plant, which is located in Dublin, about 20 miles south of Stephenville, refused to make the switch. Each bottle of Dublin Dr Pepper proudly bears the logo of Imperial Pure Cane Sugar.

But under their franchise agreement, the Dublin plant is only authorized to supply stores in the 40-square-mile area between Stephenville and Hico. The loophole is that individuals who visit the plant are allowed to purchase up to 20 cases for their private use. So diehards who are fixated on the flavor of old-fashioned cane sugar-sweetened Dr Pepper drive to Dublin to pick up their fix.

Info Dublin Dr Pepper

If driving across the state for soft drinks sounds a little obsessive, you need to consider how important a role Dr Pepper plays in some people's lives.

In cold climates, coffee is the favored caffeine delivery system, and when people talk about being addicted to the stuff, they aren't kidding. Caffeine is habit-forming, regardless of how you imbibe it.

In the warmer climate of the South, the bottomless iced tea glass is taken for granted at restaurants. But for other Southerners, the caffeinated beverage of choice is a carbonated soft drink — Coca-Cola in Georgia and Dr Pepper in Texas. Roughly speaking, a 20-ounce bottle of Coke or Dr Pepper contains as much caffeine as a five-ounce cup of coffee. Of course, some people drink Dr Pepper by the liter.

"It's an addiction," says Houston journalist Bobette Riner, who grew up drinking Dr Pepper in West Texas. She says she tries to keep her habit under control by only drinking two a day. But she is a discerning consumer. Just as Starbucks fans turn up their nose at inferior coffee, Riner prefers the taste of Dublin Dr Pepper to the "nasty corn syrup flavor" of the conventional stuff. She picks some up when she travels north to visit her family.

Riner sometimes shares a few bottles from her private stash when she needs a favor from the Dr Pepper-obsessed computer guys at work, where the soft drink is referred to as "crack." One IT guy decorated his office with empty Dr Pepper bottles, Riner said. The computer guys have reported having problems when they tried to quit drinking the stuff. (Yes, there are several Dr Pepper addiction support groups.)

Since the demand for Dublin Dr Pepper exceeds the supply, a thriving black market has sprung up. Driving around the state this spring, I noticed little paper signs in the front windows of small-town drugstores and mom-and-pop restaurants advertising the availability of Dublin Dr Pepper. I never really gave much thought to where they were getting the stuff.

That's where the bootleggers come in. At a cooking demonstration I gave this spring at the Dallas Museum of Art, I told the audience that the Dr Pepper-­marinated tenderloin recipe that I included in my The Texas Cowboy Cookbook worked a lot better if you used Dublin Dr Pepper. The cane sugar caramelizes better on the grill.

After the event, a bootlegger introduced herself. The wisecracking lady said she kept a group of small shops in her Dallas suburb supplied. It was all very hush-hush, because the bootleggers are going around the distribution rules of the bottling franchise. Each franchisee is supposed to supply its own area.

I was fascinated: Smuggling addictive soft drinks across county lines is the sort of aberrant behavior I have dedicated my life to investigating.

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It cost six bucks to get into the Dr Pepper Museum in downtown Waco. The first floor was devoted to historical information about the invention and early days of bottling and distributing the product. There was an eerie talking dummy that was supposed to look like the German pharmacist named Charles Alderton, who formulated Dr Pepper at the soda fountain of Waco's Old Corner Drug store in 1885, one year before Coca-Cola was invented.

His formula is alleged to contain 23 flavors, including natural fruit and spice essences, though the company is notoriously secretive about the actual ingredients (except to say that prune juice is not among them).

Alderton's customers called the drink a "Waco" soda, and it became quite popular at the soda fountain. The pharmacist gave the recipe to the owner of the drugstore, Wade Morrison, and the base syrup began to be made in larger quantities. When he began marketing the syrup to area drugstores, Morrison renamed the drink after Dr. Charles T. Pepper of Virginia.

Some versions of the story say the real Dr. Pepper was Morrison's girlfriend's father; others say he was a former employer. If such details matter to you, there's a Web site you can visit where the Dr Pepper catechism is carefully parsed by a fanatic named Christopher Flaherty on his Web site, Dr Pepper FAQ. You will also find stories there connecting Dr Pepper to various conspiracy theories. Lee Harvey Oswald was evidently a Dr Pepper lover.

The upper floor of the Dr Pepper Museum holds a lot of advertising materials. I sang along silently as I read the words to the "I'm a pepper, you're a pepper," jingle. And I dimly recalled the 10-2-4 campaign, which advocated the consumption of three Dr Peppers a day, at 10 a.m., 2 p.m. and 4 p.m. But I had never heard the oldest Dr Pepper slogan: "Drink a bite to eat." I also learned that the period in Dr. was dropped from the name in a logo redesign in the 1950s.