This enormous complex, operated by Arizona-based Freeport-McMoRan, is one of the world's largest open-pit copper mining operations, producing well in excess of 200 million pounds of copper a year. Traditional mining commenced on this site in 1872 and operations began to transition to open-pit mining in 1937. A fall in the price of copper in the early 1980s saw mass lay-offs resulting in the three-year long Arizona miner strike, a conflict that can still cause bitter feelings to rise to the surface in the region's bars and clubs.
If you go:
There's a viewing point overlooking the mine a few miles north of Morenci on Highway 191 (Coronado Trail Scenic Byway).
Links:

4521 US Highway 191
Morenci, Arizona 85540 USA
Phone Numbers:
+1 (928) 865-4521