Copper mining in Arizona

In Arizona, copper mining has been a major industry since the 19th century. In 2007, Arizona was the leading copper-producing state in the country, producing 750 thousand metric tons of copper, valued at $5.54 billion. Arizona's copper production was 60% of the total for the United States. Copper mining also produces gold and silver as byproducts. Byproduct molybdenum from copper mining makes Arizona the nation's second-largest producer of that metal. Although copper mineralization was found by the earliest Spanish explorers of Arizona, the territory was remote, and copper could seldom be profitably mined and shipped. Early Spanish, Mexican, and American prospectors searched for gold and silver (see Silver mining in Arizona), and ignored copper. It was not until the completion of the Southern Pacific Railroad in 1876 that copper became broadly economic to mine and ship to market.

All copper mining was done by underground methods until the early 20th century. After the Bingham Canyon mine in Utah successfully mined a large low-grade copper deposit from a large open pit, the same technique was applied to Arizona's porphyry copper deposits. Arizona's first open pit copper mine opened at Ajo in 1917.