Last Friday, Mr. Johnson was planning to hold his last dance. In 2012, he discovered that he has Parkinson’s disease, and he’s decided to put the farmstead, including Johnson’s Barn, up for sale.

“There’s been a Johnson farming this land for almost a century,” he said. “I was born the same day they moved this barn here. Mom used to put me to sleep in a cardboard box beneath the lunch counter.”

Mr. Johnson did the same with his son, Eric.

“This is all I know,” said Eric, 30, who’s been collecting cash, stamping hands and organizing morning-after cleanups for as long as he can remember. “Same with sleeping behind Dad in the tractor out in the fields when I was real little. This place is who I am.”

It has played a role in my own story as well. My grandmother was the sister of Mr. Johnson’s father, Herb. After she met my grandfather, who grew up in Dodge, N.D., they headed west, eventually settling for good in Los Angeles, where I was raised. North Dakota, though, was never far from our minds. We made regular trips back to the farm, returning home with memories of feeding pigs, jumping motorcycles over ditches and getting lost in rows of giant sunflowers. The barn was a featured attraction: home to family reunions, weddings and after-hours roller-skating. Back then, I had little sense of its importance. It wasn’t just a family haunt, but a building that over the years had become something of a CBGB for the farm set. So I set out to research this slice of my family history before the dances were a thing of the past.

In this rural pocket of the upper Midwest, Mr. Johnson’s barn dance is the only one left on a working family farm. The barn is the only place for miles that has enough room for a hundreds-strong line-dance to Steve Earle’s “Copperhead Road.” There’s no bar, so you bring your own coolers full of whiskey, beer, pop or apple juice (depending on what kind of identification you show the Cass County sheriff’s deputies hired for the night) and for $3, Brian Johnson’s wife, Becky, or their daughter, Adra, will throw a burger on an electric grill for you.