Fort Ancient, located on a high bluff overlooking the Little Miami River in Warren County, Ohio, is the largest prehistoric hilltop enclosure in the United States. Constructed by the Hopewell culture between approximately 100 BCE and 500 CE, the site features three and a half miles of continuous earthen embankments that trace the natural contours of the 126-acre plateau. These massive walls, which range from four to twenty-three feet in height, are punctuated by dozens of deliberate openings or "gateways" and enclose numerous mounds, crescent-shaped earthworks, and paved stone areas. Although early European settlers mistakenly assumed the site was a defensive fortress-and later archaeologists named a subsequent, unrelated Native American culture after it-modern research indicates the complex served primarily as a monumental social, ceremonial, and religious gathering place.

The historical and archaeological significance of Fort Ancient lies in its sophisticated engineering, astronomical alignments, and its role as a sacred landscape. The site's earthworks demonstrate a highly precise understanding of geometry and are aligned with key solar and lunar events, most notably the summer solstice sunrise. As a testament to the complex social organization and artistic expression of the Hopewell tradition, Fort Ancient was designated a National Historic Landmark in 1964 and listed on the National Register of Historic Places in 1966. Its global outstanding universal value was further recognized in 2023 when it was inscribed as a UNESCO World Heritage Site as part of the Hopewell Ceremonial Earthworks.

The Kern Effigy (33WA372), listed on the National Register of Historic Places in 1986, is a highly significant prehistoric archaeological site situated on a terrace overlooking the Little Miami River in Warren County, Ohio, near the renowned Fort Ancient Earthworks. Discovered in the mid-20th century, the site consists of a low, serpentine alignment of limestone flagstones, river cobbles, and soil. Measuring approximately 110 feet in length, it is a rare example of a "stone-paved" effigy mound, contrasting with the more common earthen effigies found throughout the Ohio Valley. Archaeological excavations have revealed that the stone structure was meticulously laid out on a prepared clay floor, indicating a highly deliberate and planned construction process.

The historical significance of the Kern Effigy lies in its immense research potential regarding the cosmological, ceremonial, and astronomical practices of Ohio's prehistoric Native American populations, particularly those of the Fort Ancient or Hopewell cultures. Researchers have identified key alignments within the stone configuration that correspond to the summer solstice sunrise, suggesting the site functioned as an astronomical observatory or a sacred space for seasonal rituals. As one of only a handful of documented stone effigies in the region, the Kern Effigy provides archaeologists with invaluable insights into the diverse ceremonial landscapes of the Eastern Woodland period and the sophisticated ways in which prehistoric societies integrated their architecture with the natural and celestial worlds.