The first Otter Tail County property on the National Register was saved due to the tireless efforts of Geneva Tweten of Fergus Falls. Phelps Mill began grinding wheat along the shore of the Otter Tail River in West Central Minnesota in 1889. A concrete dam was added in 1908. No longer used after 1931, the mill sat undisturbed with all of the original equipment left inside. Geneva Tweten spent seven years fighting to save Phelps Mill. Her idea was to create a park with the mill as its centerpeice. She lobbied county and state officials extensively to purchase the property. Enlisting the aid of such well known Minnesotans as Vice President Hubert Humphrey and Supreme Court Justice William O. Douglas, she successfully saved the mill 1965 when Otter Tail County commissioners voted to buy it and the surrounding 18 acres for $3,500. The iconic mill was added to the National Register in 1975. It has been used in state and local tourism advertising campaigns.