New Cornelia mine

The roughly circular pit is one and a half miles across at its widest point, and 1,100 feet deep at the center.

Although not generally regarded as a 'dam', the New Cornelia Mine Tailings is often cited as the largest dam structure in the United States with a volume of 7.4 billion cubic feet.

Americans claimed the location in 1854 and shipped a few loads of selected ore to Swansea, Wales, but high transportation charges left little or no profit, and the mine was abandoned.

In 1911, the Calumet and Arizona Mining Company, which already had a major operation in Bisbee, took an option to buy 70 percent of New Cornelia stock.

The mine was shut down in 1983 due to low copper prices, and a worker dispute with the local union.