The city of Sioux Falls developed at the waterfalls on the Big Sioux River, a tributary to the Missouri River, 50 miles south. Mills and a mill race were built at the site as early as the 1880s, and a 500kw power plant was constructed in 1908. Close to downtown, the Falls area was a warehouse and industrial zone for much of the 20th century. In the 1970s, a major effort to clean up the area began and led to the creation of Falls Park. Today the old Queen Bee Mill building is a rebuilt ruin in the park, and the Light and Power Company hydro plant has been converted into the Falls Overlook Café.