For immediate release

Release dated: 
June 10, 2016
Media contacts: 

Jessica Kohen, Marketing and Communications, 651-259-3148,
Tom Sanders, Jeffers Petroglyphs Historic Site, 507-628-5591,


Petroglyphs are images carved on a rock face. The word comes from the Greek “petra,” meaning stone and “glyphe,” meaning carving. Petroglyphs are found worldwide.

Ancient Rock Carvings
The rock outcrop at Jeffers Petroglyphs Historic Site is part of a 26-mile vein of pinkish Sioux quartzite that runs through prairie and farm fields in Minnesota’s Cottonwood County. It is among the world’s oldest bedrock formations, starting as sand 1.6 billion years ago and formed through enormous pressure and heat deep in the earth.

The earliest carvings at Jeffers Petroglyphs were created about 7,000 years ago. The most recent were made about 250 years ago. This long timespan makes Jeffers one of, if not the, oldest continuously used
sacred sites in the world.

In 1970 Jeffers Petroglyphs was added to the National Register of Historic Places.

Current Conservation
Careful study and interpretation of the carvings at Jeffers had identified approximately 2,000 individual petroglyphs on a part of the rock face 50 yards wide and 300 yards long. Adjoining rock was covered with lichen, an organism that is part alga, which needs sunlight to make food, and a fungus that anchors itself to the rock.

Beginning in 2006, a plan was made that would naturally remove the lichen with the least impact on the petroglyphs that might be underneath. The effort took more than five summer seasons and included covering the lichen with sun-blocking black plastic membranes, removing their source food via sunlight, and removing dead lichens with careful and repetitive mopping. The restoration team was led by site manager and archaeologist Tom Sanders, and included several archaeologists from the field and academia, their students, conservators and elders from the American Indian community.

The outcome? The number of identified carvings at Jeffers Petroglyphs more than doubled, from 2,000 to 5,000. Intensive research and discussion on the part of archaeologists and, most notably, Indian elders, has surfaced new information which confirms that American Indian ancestral leaders had
advanced knowledge of mathematics, astronomy and medicine.