See the model that inspired Buffalo Rock’s hidden modern art

At the LaSalle County Historical Society museum in downtown Utica, there’s a recently rediscovered artifact on view that shines a new light on Starved Rock Country’s connection to the world of contemporary art.

Spread across a pair of 6-foot tables, a massive plaster artist rendering that was tucked away out of view for decades now provides context for one of the region’s most important – and often overlooked – works of art.

In 1983, Edmund Thornton and the Ottawa Silica Co., in a private/public partnership with the Illinois Department of Natural Resources, commissioned renowned landscape artist Michael Heizer to design a series of large-scale earthworks at the site that would become Buffalo Rock State Park.

Collectively known as Effigy Tumuli, these five larger-than-life sculptures were constructed by backhoeing mounds of dirt into geometric shapes that resemble giant animals native to the region – creating what would become Heizer’s only site-specific representational sculptures to date.

Heizer, a contemporary of artists like Nancy Holt and Robert Smithson, rose to prominence in the late ’60s after leaving the New York City art scene to focus on crafting and documenting “negative sculptures” in the deserts of the American West.

These pieces were created by removing earth from the desert floor – resulting in famed works like “North, East, South, West” and “Double Negative” – a pair of 50-foot-deep, 1,500-foot-long trenches that can still be seen in the barren Nevada desert.

These subterranean and desolate works stand in sharp contrast to the “Effigy Tumuli” sculptures that, to the uninitiated, might be confused for naturally occurring hills covered in lush prairie grasses – an intended purpose of the artwork and land reclamation process.

Designed to pay direct homage to the indigenous mound-building cultures that had long inspired his work, Heizer’s sculptures resemble a water strider, frog, turtle, catfish and snake – and still can be seen in aerial/satellite images of the park.

The project took land once scarred by industrial mining practices and rehabilitated it into a picturesque riverfront park and a world-class piece of public art. Stewarded by local benefactor Edmund Thornton, the project was debuted to the public in 1983 with a 3D artist rendering of the site, showing the five sculptures, plus three that would ultimately not be included in the final work.

This “Earthmoving Proposal,” like the final sculptures, is massive in scale - about 12-by-4 feet. The proposal is mounted to black plywood boards and is signed and notated by Heizer himself. After Thornton died in 2023, the rendering was discovered in his foundation’s storage garage, having not seen the light of day in several decades.

Upon its discovery, the piece was donated to the LaSalle County Historical Society’s collection by Thornton’s widow, Susan Thornton, who serves on the LCHS board.

The piece is on special view in the Heritage Center until Sept. 26, celebrating Buffalo Rock and the region’s indigenous history. The work will then enter the museum’s permanent collection, where it will remain on display.

The discovery and preservation of this piece comes at a particularly important moment in Michael Heizer’s career. In 2025, his monumental sculpture “City” was completed in the remote Nevada desert and opened to the public. This monolithic work, possibly the largest piece of contemporary art ever created, began construction more than a decade before “Effigy Tumuli” was completed. “City” has brought new attention to the career of this singular artist and his land art creations - including “Effigy Tumuli.”

Next time you’re at Buffalo Rock visiting the grazing bison or taking in the picturesque vistas along the Illinois River, be sure to spend some time wandering the site of Illinois’ hidden piece of world-class art.

Buffalo Rock State Park and “Effigy Tumuli” are located at 1300 N. 27th Road in Ottawa. The park is open to the public from 8 a.m. to 7 p.m. daily.

The LaSalle County Historical Society museum is located at 101 E. Canal St. in North Utica and is open from noon to 4 p.m., Friday through Sunday.