Rock Solid

The glaciers that churned their way through central Minnesota 50,000-odd years ago ground granite and other rock formations into billions of small pieces called cobblestones. On what is now Lake Mille Lacs, eons of wind and ice have since deposited the stones along its southern shore, providing a great source of building blocks for cobblestone walls.

I’m very fond of the material, greatly preferring the baseball-sized stones to the landscaping boulders so fashionable today. I like the shadowy texture the stones create on a sunny day—just the kind of day it was when I happened upon Donald and Christina Swensons’ place on Mille Lacs. Turned out that the Swensons, who live in the Twin Cities, purchased the place about five years ago. With loving care and elbow grease, they have refurbished it for twenty-first century use.

The house dates back to 1917 when three such structures were built along the lake’s south shore. The Swensons’ place was created for a Winona banker who spared little expense on its construction. (Copper nails and flashing were used on its original slate roof.) When a fire, in 1930, significantly damaged the perimeter walls, the owner reinforced them with brick on the inside. Decades later, the Swensons didn’t appreciate the cold masonry inside, so they had the walls furred out and Sheetrocked. They kept the pine-clad walls of the inside rooms intact, insuring a warm interior glow.

The Swensons bought the stone house from Char and Bill Berger, who now live next door and happily share its history. Char, for instance, recalls the tornado scare that drove the family to the basement—a safe haven within twenty-four inches of local cobblestone walls.  

The Basics Contrary to popular belief, cobblestone refers to more than Victorian street-paving material. Among other things, cobblestones—geologists call them “erratics,” alluding to their random deposit by retreating glaciers—are markers of a geological age.

Dale Mulfinger is a partner in Sala Architects and a professor of architecture at the University of Minnesota.