Sacramento Pit copper mine at Bisbee, Arizona. This is a pit 435 feet deep. In 1911 a shaft was sunk into the slopes of the east wall. In 1917 a dynamite charge blew off the top rock of the crown and dredges were worked to excavate the pit's ore bodies. By 1931 the pit floor was too narrow for dredges to work in. The ore was taken out by caving in the walls into the lower mine levels. Between 1917 and 1931 the mine, which covers thity-five acres, yielded 20,843,667 tons of ore. The mine is today abandoned. This development by the Phelps Dodge Company by Russell Lee