I first visited the International Vinegar Museum 20 years ago. My dad was always looking for interesting things to see – and if there was a quirkiness factor, so much the better. Once he stumbled upon the museum, which sits on the main street of tiny Roslyn, South Dakota, he began drinking a small glass of vinegar each evening. He’d learned, as part of the tour there, that certain vinegars are as precious as fine wines and that some are considered curatives. He offered shots to his bewildered guests, taciturn farmers who drew their brows together and responded with a clipped “nope.”

After he died, I found yet more vinegar stuffed into cabinets, and I came to wonder: Is the stuff really that great? This summer I visited the museum twice in pursuit of vinegary magic. The scenes were what I remembered: folks stopping by on their way to or from somewhere, curious, unsure what they’d find.

“Dad, you can put the balsamic vinegar on your ice cream,” Karissa Davis says to her father, Jeff Stein. Davis has just learned that the staff of the museum loves balsamic on ice cream.

“Really?” says Stein, sounding dubious. A local named Fran Rougemont, who is working at the museum today as a guide, tells the family that she loves cooking with vinegar, too, using it with pies and fish.

Davis, Stein and Stein’s wife, Shirley, express surprise, as most people would. The family has stopped by the vinegar museum – which claims to be the only one like it in the world – on their way home from a wedding. Today’s tour highlight: a free vinegar tasting.

The museum is housed in the town’s former auditorium. The brick structure with hardwood floors was built in the 1930s by the Works Progress Administration. It boasts many flavored varieties of vinegar (pecan, maple, etc.), along with exhibits on the history of the sour substance. About 300 bottles are on display from around the world, including a tiny bottle of balsamic that has been aged 25 years and retails elsewhere for more than $100.

Placards provide information about vinegar that few would know: It has been used in combating head lice and as a weed killer; the Babylonians were making vinegar more than 5,000 years ago. On display are pieces of pottery, which the museum’s founder, Lawrence Diggs, made using a vinegar infusion of his own creation – earning the museum a mention in a 2005 New York Times article. In a small gift section, visitors can buy their own bottles and find a T-shirt that says, “I got pickled at the International Vinegar Museum.”

Alexandra Buyalos, left, and Megan Rogers, both from Baltimore, sample the collection at the International Vinegar Museum. Photo for The Washington Post by Jay Pickthorn

Roslyn is a town of fewer than 200 people that sits in northeastern South Dakota, among fields of corn and soybeans and rolling prairie hills, a landscape dotted with small glacial lakes. Before the museum opened in 1999, the town’s biggest claim to fame was that it was the birthplace of Myron Floren, the accordionist on “The Lawrence Welk Show.” It is not on a major highway and is hours from any major metropolitan area. Despite that, folks at the museum tell me it attracts about a thousand visitors each year. Pins cover a world map on the wall, showing where visitors hail from.

The most common questions people have about vinegar, Diggs tells me, are: What is vinegar? And what is it made of? Simply put, vinegar comes from anything that has alcohol in it; bacteria turn the alcohol into acetic acid. That alcohol, in turn, can be made from anything that has starch or sugar – including unexpected sources such as honey, potatoes or beets. You can also make vinegar out of cocoa pulp. “There are people who make and swear by milk vinegar,” Diggs says. “Not me.”

Diggs, now 73, became fascinated with vinegar while taking food science classes at San Francisco State University in the 1980s. The research led him to self-publish a book on the subject. He came to Roslyn in 1989, seeking a quiet summer place where he could write. Before then, he had spent most of his life in San Francisco. He served in the Peace Corps in Africa and was a radio reporter and bus driver. Today he works with incarcerated men and is an artist-in-residence for the South Dakota Arts Council. He also consults on vinegar with clients around the world.

The museum’s shelves are lined with an array of styles of vinegar. Photo for The Washington Post by Jay Pickthorn

The museum, he says, was a Hail Mary pass for the town, which was looking for something to draw people to the area. In the late 1990s, some residents formed a committee called Community Advancement for Roslyn and Eden (Eden is a small town nearby), or CARE. Ultimately, they realized they needed to do something with the resources they had, and something that was totally different from anything any other town was doing. Diggs was that resource: He had both knowledge and several dozen bottles of vinegar from his consulting business. Voilà: a vinegar museum.

Diggs tells me that he agreed to help start the place, but he wanted it to be community-focused: “It’s not going to be about me.” Twenty-two years on, the museum is managed by CARE and staffed by people who got on-the-job training about vinegar. And it is the town’s biggest draw. Roslyn has an annual Vinegar Festival, replete with a “royal quart,” including a vinegar queen. The museum is open Thursday through Saturday, and only in the summer, but Rougemont says someone’s generally available if you ask for a tour. She recounts a time she was riding her bike to pick up her mail from the post office, and a family in a big RV asked if they could get a tour. “I told them I just needed to run home and grab my key,” she says.

At the museum, by the time Rougemont asks if the Stein family is interested in doing a tasting, Karissa Davis and her mom, Shirley, are game. Jeff Stein isn’t so sure. “C’mon, Dad,” says Davis. “Don’t be chicken.” Stein makes his way to the tasting table, where Rougemont is waiting with several bottles of vinegar. Small glasses hold samples of wild blueberry, black fig, maple, tequila lime, spiced pecan and two kinds of balsamic.

Rougemont explains the process, which is much like tasting wine: You look at the vinegar and swirl it to release its “volatiles.” You then use a long, wooden cotton swab to capture the liquid, which is placed on the tongue and roof of the mouth. “Wow, I’m surprised,” Jeff says after trying a bit of the pecan vinegar. “You can really taste pecan. I was expecting sour-sour, and it’s not. I was expecting something completely different.”