For 125 years, the Homestake Mine in Lead, South Dakota, founded by the mining magnate George Hearst, was the largest and deepest mine in the Western Hemisphere, and the most productive gold mine in recorded history. In the end, more than 40 million ounces of gold were extracted from the massive underground complex. The mine ceased operations in 2002, but in recent years its deep underground chambers have become home the Sanford Underground Research Facility and some of the most sophisticated physics experiments in the world.