Hidden Thunder - Rock Art of the Upper Midwest

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Renowned watercolor artist Geri Schrab and archaeologist Robert “Ernie” Boszhardt team up in Hidden Thunder to unveil an up-close-and-personal look at American Indian rock art. With an eye toward preservation, Schrab and Boszhardt take you with them as they research, document, and interpret the ancient petroglyphs and pictographs made by Native Americans in past millennia. In addition to publicly accessible sites such as Wisconsin’s Roche- a-Cri State Park and Minnesota’s Jeffers Petroglyphs, Hidden Thunder covers the artistic treasures found at several remote and inaccessible rock art sites in the Upper Midwest—revealing the ancient stories through words, full-color photographs, and Schrab’s watercolor renditions.

Offering the dual perspectives of scientist and artist, Boszhardt shares the facts that archaeologists have been able to establish about these important artifacts of our early history, while Schrab offers the artist’s experience, describing her emotional and creative response upon encountering and painting these sites. Viewpoints by members of the Menominee, Ho-Chunk, Ojibwe, and other Native nations offer additional insight on the historic and cultural signifi- cance of these sites. Together these myriad voices reveal layers of meaning and cultural context that emphasize why these fragile resources—often marred by human graffiti and mishandling or damage from the elements—need to be preserved.


“The images, visions and fantastic works of art painted and carved by American Indians hundreds of years ago still carry power, foster intrigue, elicit spiritual and emotional responses, and create dreams for the future and visions of the past.  In Hidden Thunder Ernie Boszhardt and Geri Schrab take readers on an inspiring journey of discovery and enlightenment to these places of enduring value. ”  -John Broihahn, Wisconsin State Archaeologist


“The powerful ancient drawings stand with great meaning to those who undestand the symbolism, and it saddens me that many of the existing sites have been and are continually being vandalized.  We are grateful for the work being done by Ernie and Geri to preserve in some way what our ancestors have left behind.” – Joey Awonohopay, Director Language and Culture for the Menominee Tribe of Wisconsin.


Hidden Thunder embodies a story written on sandstone.”  – Truman Lowe


Hidden Thunder sets a new standard for rock art books by combining respect with a deep appreciation of indigenous art left on cliffs, rock shelters and cave walls in the upper Midwest. Fittingly, the high production standards of the book—evident in the design, layout and content—are balanced by the thorough, interpretative text. The dry, academic jargon found in so many rock art studies has been abandoned for rich, descriptive text that retains scientific vigor that we can understand. The alternating writing, by a seasoned archaeologist and a perceptive, accomplished artist, provides complementary descriptions and understandings for each site. The archaeologist guides us through the clues to age and identity of sites and images, while the artist shares in words her in–depth visual palette. Most importantly, both authors display their respectful feelings for the indigenous art.

Personal experiences at the rock art sites are mixed with scientific observations to produce a balanced understanding of the art and the often-sacred spaces. Ancient Native Americans deliberately left this durable art, so filled with spiritual and cultural references, to inform us about the sacred landscape that we now share.

What better way is there to appreciate this precious cultural heritage than to use the living voices of Native Americans descended from the shaman–artists who painted the intriguing images? Each chapter culminates with an extended statement by an insightful Native American.

Hidden Thunder provides us with a balanced look at the topic of rock art. Importantly, we gain a sense of place through colour photographs before entering the sacred spaces. Clear photographs of the ancient images also benefit from skilled watercolour paintings of the same images. The watercolours in a sense restore some emotion to the ancient art.

Hidden Thunder is an essential book that opens a new path for appreciating rock art and sets a standard for describing a complex subject.”     – Thor Conway, Author of five books, including Painted Dreams, and Spirits on Stone

Hidden Thunder, Rock Art Of The Upper Midwest