 Park management fell to the state of Wyoming in 1957.Lake Guernsey State Park (also known as Guernsey State Park Historic District, Lake Guernsey Park, Guernsey Lake Park, or Guernsey State Park) was declared a National Historic Landmark District in 1997 for its design history and construction.The park's design was the result of the first collaboration between the National Park Service and the Bureau of Reclamation, and its infrastructure was built by Civilian Conservation Corps crews.