One of the more unusual groups of effigy mounds built by Wisconsin’s Native Americans during the Late Woodland Period is located in this park. Situated on a low plateau at the headwaters of the North Branch of the Milwaukee River, the group originally contained approximately sixty mounds, dominated by long-tailed effigies that early investigators thought were lizards. Actually they are water spirits or underground water panthers, symbols that were especially common in eastern Wisconsin, with its abundance of lakes, rivers, streams, and wetlands. Although there are no major bodies of water near here, the plateau is surrounded by springs, which are entrances to the underworld of the water spirits in many Native American cosmologies. Over the years many mounds were obliterated by cultivation or otherwise reduced to invisibility. When archaeologist Kermit Fleckman mapped this site in 1941, only thirty-one of the original sixty mounds remained. In 1950 the state purchased the site for a park (now a county park) and restored some mounds damaged by looting. The preserved group includes five conical, one oval, and eight linear mounds, two tapering linears, two symmetrically paired bird effigies, and eleven panther effigies. They vary in length but are typically about 3.5 feet high. The largest is a panther 250 feet long.