Willow River State Park, a 2,891-acre park north of Hudson, is known for Willow Falls, a powerful cascade in a gorge about 200 feet deep, and for Little Falls Lake on the Willow River. The area also preserves deep natural and human history, from trilobite fossils in rock around 600 million years old to Santee Sioux and Ojibwe use of the region and a battle recorded there in 1795. By 1830, logging and wheat farming had reshaped the valley, and the river later powered mills and hydroelectric plants that supplied Hudson. After utility ownership ended, the land became a state park in 1971.