Rocks That Teach: Cranbrook Institute of Science and the Sanilac Petroglyphs

Some say there are no coincidences in life, and in my many years of genealogical and historical research, I have found that perhaps a better word for these types of experiences is serendipity.  Often I find myself researching a certain topic and “by chance” I run into an expert standing next to me in line at the grocery store.  The other day just such a happenstance occurred.  I was invited to a lunch and who should sit next to me but Stacy Tchorzynski, an Archaeologist for Michigan’s State Historic Preservation Office and Department of Natural Resources.  She asked me if the Cranbrook Archives had any materials on the Sanilac Petroglyphs and we launched into a discussion about the importance of documenting and preserving Michigan’s only known prehistoric rock carvings.  Located in an historic state park covering 240 acres, the petroglyphs, which were carved into very soft sandstone, have eroded over time and weather exposure.   In addition, 19th and 20th century vandalism and graffiti have further degraded the carvings.


Sanilac Petroglyphs, Cass City, MI, 1945. Cranbrook Archives.

Cranbrook has had a long interest in the petroglyphs—in the 1940s, the director of Cranbrook Institute of Science (Dr. Robert Hatt) worked with the DNR and University of Michigan’s Museum of Anthropology to develop a preservation plan for the rock carvings.  In fact, Hatt’s 1942 report even suggested that the site would make an “excellent State Park” and that the main group of petroglyphs should be fenced off.  In 1958, the Institute of Science published a monograph on the petroglyphs followed in 1965 by a collaborative meeting between the Institute, the Michigan Archeological Society, and the Sanilac County Historical Society.   This meeting resulted in the acquisition of the 80-acre site by the Michigan Archeological Society.


Cranbrook Institute of Science Educational Field Trip at the Sanilac Petroglyphs in Cass City, MI, circa 1968. Cranbrook Archives.

The site of the Sanilac Petroglyphs is also an important ceremonial site for the Anishinabek – the petroglyphs are very powerful places of learning and spirituality for them and are referred to as “rocks that teach.” 

Through the 1960s and 1970s, Cranbrook Institute of Science sponsored field trips to the site for its members.   Drawings of the petroglyphs, part of the collection of the Institute of Science, will soon be on display as part of the exhibition My Brain Is in My Inkstand: Drawing as Thinking and Process at the Cranbrook Art Museum.

~Leslie S. Edwards, Head Archivist

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