In Hidden Thunder, renowned watercolor artist Geri Schrab and archaeologist Robert "Ernie" Boszhardt give readers an up-close-and-personal look at rock art. With an eye toward preservation, Schrab and Boszhardt take you with them as they research, document, and interpret at the ancient petroglyphs and pictographs made my 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—revealing the ancient stories through words, full-color photographs, and artistic renditions.

Offering the duo 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 significance 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 most common relics of the 12,000-year occupancy of the Upper Mississippi River Valley may be the chipped stone projectile points that Native Americans fastened to the ends of their spears, darts, and arrow shafts. This useful guide provides a key to identifying the various styles of points found along the Upper Mississippi River in the Driftless region stretching roughly from Dubuque, Iowa, to Red Wing, Minnesota, but framed within a somewhat larger area extending from the Rock Island Rapids at the modern Moline-Rock Island area to the Falls of St. Anthony at Minneapolis-St. Paul.

Logging tens of thousands of miles and visiting private collectors from all walks of life since 1982, Robert Boszhardt has documented thousands of projectile points found in this region. In addition to drawings of each style, he provides other accepted names as well as names of related points, age, distribution, a description (including length and width), material, and references for each type. The guide is meant for the many avocational archaeologists who collect projectile points in the Upper Midwest and will be a useful reference tool for professional field archaeologists as well.

Emphasizing the preservation of sites as well as a mutual exchange of information between professional and avocational archaeologists, this guide will reveal projectile points as clues to the past, time markers which embody crucial information about the cultures of the Mississippi River Valley's early inhabitants.