Sultan residents participated a civic improvement program during the 1950s and 1960s that upgraded or replaced several major facilities, often with assistance from the state government. A new city hall was opened in 1954, the elementary school was expanded in 1957, and a new landing field for airplanes and helicopters opened in 1958. The city annexed of rural land to the southeast in 1958 and it was subsequently developed for housing. The Skykomish River Bridge was also replaced by a new span in 1961. The Snohomish County Public Utility District (PUD) constructed the Culmback Dam on the Sultan River, creating the Spada Lake reservoir and providing electricity and drinking water for Everett and much of the county beginning in 1965.