It’s rare when a structure and a person become so inseparable that it’s difficult for people to think of one and not the other.

But that’s the way it was, for at least the past half-century, with Gustave Clark and the historic Dells Mill near Augusta, Wis., about two hours east of the Twin Cities.

Clark, the mill’s owner and tour guide, had managed the scenic property on the banks of the Dells Mill Pond since 1964 and had been giving tours of the facility since 1968. Four generations of his family have lived at the mill since 1894.

Clark’s sister, Nancy Scobie of Chippewa Falls, Wis., summed up the relationship this way: “Gus was the mill, and the mill was Gus.”

But the mill lost its popular operator when Clark died in his sleep from heart-related ailments on Sunday. He was 71.

His death leaves the future of the 150-year-old mill in doubt, although Scobie vows to do everything in her power to keep it open and accessible to visitors.

Long considered one of the most photographed spots in Wisconsin, the mill operated continuously until 1968 and continued to clean grain until eight years ago. It is listed on the National Register of Historic Places. Photos of the classic red structure on the banks of the pristine mill pond have graced countless calendars and book covers, and Reader’s Digest once ranked it as one of the top places to visit in Wisconsin.

Dells Mill, located on Wisconsin Hwy. 12 north of Osseo, began in 1864 grinding the wheat that dominated Wisconsin’s Civil War-era economy. The mill’s history drove Clark’s passion and inspired his tours.

Dressed in a Civil War uniform, Clark would entertain kids by demonstrating how to fire an antique muzzleloader rifle, singing Civil War songs while playing his homemade “git-fiddle” (a cross between a guitar and a banjo) and telling stories about the past.

Gloria Cowan, a retired teacher from Chippewa Falls, Wis., fondly recalled leading groups of second-graders on field trips to the mill for at least two decades beginning in the mid-1970s.

“The kids loved it, and they couldn’t wait to get to second grade so they could go down to the mill,” Cowan said.

“It was a fun way for the kids to learn about history.”

While she hasn’t yet formulated a long-term plan, Scobie said she knows one thing for sure: “I am dedicated to keeping my brother’s dream alive.”

In the short term, Scobie said, the mill’s public hours will be scaled back. Clark, whom his sister called a “one-man show,” was on site to greet visitors from 10 a.m. to 5 p.m. seven days a week from May through October. The mill will be open from noon to 5 p.m. Saturdays and Sundays, plus Labor Day, until the end of October.

“We’re dealing with a historical site,” Scobie said. “How do you work to make it not just one person’s responsibility or even one family’s responsibility? Those are the big questions right now.”

Services for Clark have been held.