Cornelia Mine and Tailings Pile, Arizona

One of the largest mine tailings piles in the world at 7.4 billion cubic feet, the New Cornelia Tailings is often cited as the largest dam structure in the country by volume (the tailings, waste material from the mining process, were heaped into a pile which created a holding structure for future tailings, some of which were deposited in a pumped slurry, thus the tailings pile is an impoundment or dam.) The mine that produced the tailings, the 1.5 mile wide open pit New Cornelia Mine, is owned by Freeport-McMoRan, who ceased mining operations in 1984, ultimately shuttering the smelter in 1985. Located in the remote town of Ajo, Arizona.