Anglo Invasion and Discoveries: 1848-1886

The Anglo-American invasion of the Southwest began as a trickle, with a few fur trappers and adventurers arriving via Santa Fe in the 1820s. It picked up with the US victory over Mexico in the war of 1847 and the latter’s cession of large swaths of the West to the US in the treaty of Guadalupe Hidalgo and the Gadsden Purchase. It was interrupted temporarily by the Civil War and turned into a flood by the 1870s. At this time, the US Military began a systematic policy of containment of Native Americans on reservations, with extermination of those (especially the Navajo and Apache) that did not conform to this. Native resistance ended with the surrender of Apache raider Geronimo to Gen. Nelson Miles at Skeleton Canyon, in SE Arizona, in 1886.

Figure 9. Graphical history of copper mining in SW N America

Most of the major mineral districts of the Southwest were discovered during this period (figure 9), many by US Army troops traversing the area during the Civil War and afterwards, searching for and fighting the Apache. Morenci, for example, entered history in reports from General Carleton’s California Volunteers who, in 1863, noted strongly copper stained outcrops along Chase Creek above its junction with the San Francisco River.

Copper was initially of only marginal interest to Anglo-American prospectors and miners, due to high transportation costs versus its low unit value. It was more useful as a visual indicator of the presence of precious metals deposits, then as a by-product of their exploitation.

As railroads were constructed into Southwestern North America, freight costs dropped and copper deposits became economically viable. Early mining was by small-scale underground stoping methods, with copper recovery by direct-smelting of high-grade oxides. As grades dropped, ores were concentrated by gravity methods then smelted. The completion of the Southern Pacific Railroad across southern Arizona, in 1885, allowed for cheap trans-continental transportation of ores, concentrates and supplies. This allowed lower grade ores to be worked and made exploitation of all deposits more profitable.