Moraine Hills State Park in McHenry County preserves a broad Fox River landscape around McHenry Dam and Lake Defiance, shaped by glacial terrain. Its development began with the construction of the McHenry Dam in 1907, which was donated to the state in 1924 and replaced by a new dam in 1934. The first park unit, then called McHenry Dam State Park, was established in 1939 with the purchase of fifteen acres on the river’s east bank. Expansion continued through later land donations, property acquisitions around Lake Defiance, and added facilities, leading to the park’s reopening as Moraine Hills State Park in October 1976.