The Ajo Mining District

The Ajo Mining District. . Americans first worked the copper deposits at Ajo in 1854, one year after the Gadsden Purchase. These early American miners found abandoned workings and crude mining tools as mute evidence of earlier mining in the district., During the next half century mining was confined to veins and other small bodies of high grade copper ore. Some ore was transported by mule train across the desert to Yuma for shipment to smelters in Swansea, Wales. Much of the mineralized ground in the district was staked for mining claims and several mining companies were formed., An intensive diamond drilling campaign started in 1911 proved the existence of a large body of low grade copper ore and resulted in the construction of a leaching plant by the New Cornelia Copper Company for treatment of the ore. The plant went into operation in May, 1917 and initiated large scale exploitation of the land copper deposits. . This historical marker is in Ajo in Pima County Arizona