Glaciers as tall as the Willis Tower, one thousand four hundred fifty feet or one hundred ten stories, moved everything in their path, and some of the rocks here came from as far north as Canada. As the Wisconsin Glacier retreated, it left moraines, kames, and kettles, and large masses of ice broke off as meltwater formed Lake Defiance. Moraines are long hills made of glacial till, including sand, gravel, silt, clay, and boulders, and this loose formation of rocks allows water to penetrate and flow in streams above and underground. By twelve thousand B.C.E., the glacier had retreated, by nine thousand B.C.E. the first people used this site, and by four thousand B.C.E. Potawatomi, Sauk, and Fox tribes used it. In the early eighteen thirties, Horace Long built a home on the southeast corner of the park. McHenry Dam was built in nineteen oh seven, including a hand-operated lock, and a new concrete block dam replaced it in nineteen thirty-four. In nineteen thirty-nine, the State of Illinois acquired land for McHenry Dam State Park; in the nineteen sixties, the Division of Water Resources managed locks on park property west of the Fox River; in nineteen seventy-one, the state acquired two thousand two hundred acres including Lake Defiance; in nineteen seventy-five, park facilities were constructed; and in nineteen seventy-six, Moraine Hills State Park had its grand opening. From the nineteen nineties through today, volunteers have worked with staff to restore natural areas, and in two thousand seven, Friends of Moraine Hills State Park was founded to promote awareness and support the park. Kames are mounds of sand and gravel deposited by running water along the edge of retreating ice, Lake Defiance is a kettle lake that has been filling with peat for thousands of years, peat is soil made of partially decomposed plants, and wetlands including marshes, fens, and bogs make up about half of the park's two thousand two hundred acres.